diff --git a/CHANGELOG.md b/CHANGELOG.md
index cb082d27724ee58f1a2c09e3ecf8d2d056065fa3..c7739c5b4af74b2d12f92d87c864d775b82e9262 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -42,6 +42,7 @@ Please mark all change in change log and use the ticket from JIRA.
 - \#599 - Build index log is incorrect
 - \#602 - Optimizer specify wrong gpu_id
 - \#606 - No log generated during building index with CPU
+- \#631 - FAISS isn't compiled with O3 option
 
 ## Feature
 - \#12 - Pure CPU version for Milvus
diff --git a/core/src/index/cmake/ThirdPartyPackagesCore.cmake b/core/src/index/cmake/ThirdPartyPackagesCore.cmake
index 624f1f422ec6a0bae6a0b2dbd70f6cf07ff769ca..9c9187d2ccb61ea57e60f6acfb072c81e1a252f8 100644
--- a/core/src/index/cmake/ThirdPartyPackagesCore.cmake
+++ b/core/src/index/cmake/ThirdPartyPackagesCore.cmake
@@ -708,7 +708,7 @@ macro(build_faiss)
     set(FAISS_CONFIGURE_ARGS
             "--prefix=${FAISS_PREFIX}"
             "CFLAGS=${EP_C_FLAGS}"
-            "CXXFLAGS=${EP_CXX_FLAGS} -mavx2 -mf16c"
+            "CXXFLAGS=${EP_CXX_FLAGS} -mavx2 -mf16c -O3"
             --without-python)
 
     if (FAISS_WITH_MKL)