diff --git a/source/client/src/clientSml.c b/source/client/src/clientSml.c
index 884756ced91bc797d8cd715337c598343ae6752d..f6f8db859075dd8accff0e21efed38fc7ec0bb46 100644
--- a/source/client/src/clientSml.c
+++ b/source/client/src/clientSml.c
@@ -714,25 +714,31 @@ static bool smlIsNchar(const char *pVal, uint16_t len) {
 
 static int64_t smlGetTimeValue(const char *value, int32_t len, int8_t type) {
   char *endPtr = NULL;
-  double ts = (double)strtoll(value, &endPtr, 10);
+  int64_t tsInt64 = strtoll(value, &endPtr, 10);
   if(value + len != endPtr){
     return -1;
   }
+  double ts = tsInt64;
   switch (type) {
     case TSDB_TIME_PRECISION_HOURS:
       ts *= (3600 * 1e9);
+      tsInt64 *= (3600 * 1e9);
       break;
     case TSDB_TIME_PRECISION_MINUTES:
       ts *= (60 * 1e9);
+      tsInt64 *= (60 * 1e9);
       break;
     case TSDB_TIME_PRECISION_SECONDS:
       ts *= (1e9);
+      tsInt64 *= (1e9);
       break;
     case TSDB_TIME_PRECISION_MILLI:
       ts *= (1e6);
+      tsInt64 *= (1e6);
       break;
     case TSDB_TIME_PRECISION_MICRO:
       ts *= (1e3);
+      tsInt64 *= (1e3);
       break;
     case TSDB_TIME_PRECISION_NANO:
       break;
@@ -743,7 +749,7 @@ static int64_t smlGetTimeValue(const char *value, int32_t len, int8_t type) {
     return -1;
   }
 
-  return (int64_t)ts;
+  return tsInt64;
 }
 
 static int64_t smlGetTimeNow(int8_t precision) {
diff --git a/source/client/test/smlTest.cpp b/source/client/test/smlTest.cpp
index eeab844712eac59edf3bb689d1c7c2afb438e8fa..d9a81ad3e67e9a7ed793345a061eb94eb6e05439 100644
--- a/source/client/test/smlTest.cpp
+++ b/source/client/test/smlTest.cpp
@@ -1188,3 +1188,36 @@ TEST(testCase, smlParseTelnetLine_diff_json_type2_Test) {
   destroyRequest(request);
   smlDestroyInfo(info);
 }
+
+TEST(testCase, sml_TD15662_Test) {
+  TAOS *taos = taos_connect("localhost", "root", "taosdata", NULL, 0);
+  ASSERT_NE(taos, nullptr);
+
+  TAOS_RES *pRes = taos_query(taos, "create database if not exists db_15662 precision 'ns'");
+  taos_free_result(pRes);
+
+  pRes = taos_query(taos, "use db_15662");
+  taos_free_result(pRes);
+
+  SRequestObj *request = (SRequestObj *)createRequest((STscObj *)taos, NULL, NULL, TSDB_SQL_INSERT);
+  ASSERT_NE(request, nullptr);
+
+  SSmlHandle *info = smlBuildSmlInfo(taos, request, TSDB_SML_LINE_PROTOCOL, TSDB_SML_TIMESTAMP_NANO_SECONDS);
+  ASSERT_NE(info, nullptr);
+
+  const char *sql[] = {
+      "iyyyje,id=iyyyje_41943_1303,t0=t,t1=127i8,t2=32767i16,t3=2147483647i32,t4=9223372036854775807i64,t5=11.12345f32,t6=22.123456789f64,t7=\"binaryTagValue\",t8=L\"ncharTagValue\" c0=false,c1=127i8,c2=32767i16,c3=2147483647i32,c4=9223372036854775807i64,c5=11.12345f32,c6=22.123456789f64,c7=\"binaryColValue\",c8=L\"ncharColValue\",c9=7u64 1626006833639000000",
+  };
+  int ret = smlProcess(info, (char **)sql, sizeof(sql) / sizeof(sql[0]));
+  ASSERT_EQ(ret, 0);
+
+  // case 1
+  TAOS_RES *res = taos_query(taos, "select * from t_a5615048edae55218a22a149edebdc82");
+  ASSERT_NE(res, nullptr);
+
+  TAOS_ROW row = taos_fetch_row(res);
+  int64_t ts = *(int64_t*)row[0];
+  ASSERT_EQ(ts, 1626006833639000000);
+
+  taos_free_result(res);
+}
\ No newline at end of file
diff --git a/source/common/src/ttime.c b/source/common/src/ttime.c
index c2892c070f42fcff9324814a5486a6b191d667a3..62a71796262314d40a3f984b3933376370110605 100644
--- a/source/common/src/ttime.c
+++ b/source/common/src/ttime.c
@@ -374,39 +374,135 @@ char getPrecisionUnit(int32_t precision) {
 }
 
 int64_t convertTimePrecision(int64_t time, int32_t fromPrecision, int32_t toPrecision) {
-  assert(fromPrecision == TSDB_TIME_PRECISION_MILLI || fromPrecision == TSDB_TIME_PRECISION_MICRO ||
+  assert(fromPrecision == TSDB_TIME_PRECISION_MILLI ||
+         fromPrecision == TSDB_TIME_PRECISION_MICRO ||
          fromPrecision == TSDB_TIME_PRECISION_NANO);
-  assert(toPrecision == TSDB_TIME_PRECISION_MILLI || toPrecision == TSDB_TIME_PRECISION_MICRO ||
+  assert(toPrecision == TSDB_TIME_PRECISION_MILLI ||
+         toPrecision == TSDB_TIME_PRECISION_MICRO ||
          toPrecision == TSDB_TIME_PRECISION_NANO);
-  static double factors[3][3] = {{1., 1000., 1000000.}, {1.0 / 1000, 1., 1000.}, {1.0 / 1000000, 1.0 / 1000, 1.}};
-  return (int64_t)((double)time * factors[fromPrecision][toPrecision]);
+  double tempResult = (double)time;
+  switch(fromPrecision) {
+    case TSDB_TIME_PRECISION_MILLI: {
+      switch (toPrecision) {
+        case TSDB_TIME_PRECISION_MILLI:
+          return time;
+        case TSDB_TIME_PRECISION_MICRO:
+          tempResult *= 1000;
+          time *= 1000;
+          goto end_;
+        case TSDB_TIME_PRECISION_NANO:
+          tempResult *= 1000000;
+          time *= 1000000;
+          goto end_;
+      }
+    } // end from milli
+    case TSDB_TIME_PRECISION_MICRO: {
+      switch (toPrecision) {
+        case TSDB_TIME_PRECISION_MILLI:
+          return time / 1000;
+        case TSDB_TIME_PRECISION_MICRO:
+          return time;
+        case TSDB_TIME_PRECISION_NANO:
+          tempResult *= 1000;
+          time *= 1000;
+          goto end_;
+      }
+    } //end from micro
+    case TSDB_TIME_PRECISION_NANO: {
+      switch (toPrecision) {
+        case TSDB_TIME_PRECISION_MILLI:
+          return time / 1000000;
+        case TSDB_TIME_PRECISION_MICRO:
+          return time / 1000;
+        case TSDB_TIME_PRECISION_NANO:
+          return time;
+      }
+    } //end from nano
+    default: {
+      assert(0);
+      return time;  // only to pass windows compilation
+    }
+  } //end switch fromPrecision
+end_:
+  if (tempResult >= (double)INT64_MAX) return INT64_MAX;
+  if (tempResult <= (double)INT64_MIN) return INT64_MIN;  // INT64_MIN means NULL
+  return time;
 }
 
+// !!!!notice:there are precision problems, double lose precison if time is too large, for example: 1626006833631000000*1.0 = double = 1626006833631000064
+//int64_t convertTimePrecision(int64_t time, int32_t fromPrecision, int32_t toPrecision) {
+//  assert(fromPrecision == TSDB_TIME_PRECISION_MILLI || fromPrecision == TSDB_TIME_PRECISION_MICRO ||
+//         fromPrecision == TSDB_TIME_PRECISION_NANO);
+//  assert(toPrecision == TSDB_TIME_PRECISION_MILLI || toPrecision == TSDB_TIME_PRECISION_MICRO ||
+//         toPrecision == TSDB_TIME_PRECISION_NANO);
+//  static double factors[3][3] = {{1., 1000., 1000000.}, {1.0 / 1000, 1., 1000.}, {1.0 / 1000000, 1.0 / 1000, 1.}};
+//  ((double)time * factors[fromPrecision][toPrecision]);
+//}
+
+
+// !!!!notice: double lose precison if time is too large, for example: 1626006833631000000*1.0 = double = 1626006833631000064
 int64_t convertTimeFromPrecisionToUnit(int64_t time, int32_t fromPrecision, char toUnit) {
   assert(fromPrecision == TSDB_TIME_PRECISION_MILLI || fromPrecision == TSDB_TIME_PRECISION_MICRO ||
          fromPrecision == TSDB_TIME_PRECISION_NANO);
-  static double factors[3] = {1000000., 1000., 1.};
+  int64_t factors[3] = {NANOSECOND_PER_MSEC, NANOSECOND_PER_USEC, 1};
+  double tmp = time;
   switch (toUnit) {
-    case 's':
-      return time * factors[fromPrecision] / NANOSECOND_PER_SEC;
+    case 's':{
+      tmp /= (NANOSECOND_PER_SEC/factors[fromPrecision]);     // the result of division is an integer
+      time /= (NANOSECOND_PER_SEC/factors[fromPrecision]);
+      break;
+    }
     case 'm':
-      return time * factors[fromPrecision] / NANOSECOND_PER_MINUTE;
+      tmp /= (NANOSECOND_PER_MINUTE/factors[fromPrecision]);  // the result of division is an integer
+      time /= (NANOSECOND_PER_MINUTE/factors[fromPrecision]);
+      break;
     case 'h':
-      return time * factors[fromPrecision] / NANOSECOND_PER_HOUR;
+      tmp /= (NANOSECOND_PER_HOUR/factors[fromPrecision]);    // the result of division is an integer
+      time /= (NANOSECOND_PER_HOUR/factors[fromPrecision]);
+      break;
     case 'd':
-      return time * factors[fromPrecision] / NANOSECOND_PER_DAY;
+      tmp /= (NANOSECOND_PER_DAY/factors[fromPrecision]);     // the result of division is an integer
+      time /= (NANOSECOND_PER_DAY/factors[fromPrecision]);
+      break;
     case 'w':
-      return time * factors[fromPrecision] / NANOSECOND_PER_WEEK;
+      tmp /= (NANOSECOND_PER_WEEK/factors[fromPrecision]);    // the result of division is an integer
+      time /= (NANOSECOND_PER_WEEK/factors[fromPrecision]);
+      break;
     case 'a':
-      return time * factors[fromPrecision] / NANOSECOND_PER_MSEC;
+      tmp /= (NANOSECOND_PER_MSEC/factors[fromPrecision]);    // the result of division is an integer
+      time /= (NANOSECOND_PER_MSEC/factors[fromPrecision]);
+      break;
     case 'u':
-      return time * factors[fromPrecision] / NANOSECOND_PER_USEC;
+      // the result of (NANOSECOND_PER_USEC/(double)factors[fromPrecision]) maybe a double
+      switch (fromPrecision) {
+        case TSDB_TIME_PRECISION_MILLI:{
+          tmp *= 1000;
+          time *= 1000;
+          break;
+        }
+        case TSDB_TIME_PRECISION_MICRO:{
+          tmp /= 1;
+          time /= 1;
+          break;
+        }
+        case TSDB_TIME_PRECISION_NANO:{
+          tmp /= 1000;
+          time /= 1000;
+          break;
+        }
+      }
+      break;
     case 'b':
-      return time * factors[fromPrecision];
+      tmp *= factors[fromPrecision];
+      time *= factors[fromPrecision];
+      break;
     default: {
       return -1;
     }
   }
+  if (tmp >= (double)INT64_MAX) return INT64_MAX;
+  if (tmp <= (double)INT64_MIN) return INT64_MIN;
+  return time;
 }
 
 int32_t convertStringToTimestamp(int16_t type, char *inputData, int64_t timePrec, int64_t *timeVal) {