diff --git a/imperative/python/megengine/quantization/observer.py b/imperative/python/megengine/quantization/observer.py
index dbeaf821b0b744cfbae347ae4f61a912c0a3fa71..381884ae9885a7c448444114653fd90ae2f530ee 100644
--- a/imperative/python/megengine/quantization/observer.py
+++ b/imperative/python/megengine/quantization/observer.py
@@ -26,9 +26,10 @@ logger = get_logger(__name__)
 
 class Observer(Module, QParamsModuleMixin):
     r"""
-    A base class for Observer Module.
+    A base class for Observer Module. Used to record input tensor's statistics for
+    quantization.
 
-    :param dtype: a string indicating to collect scale and zero_point of which dtype.
+    :param dtype: a string indicating which dtype to collect scale and zero_point of.
     """
 
     def __init__(self, dtype: Union[str, QuantDtypeMeta], **kwargs):
@@ -72,6 +73,14 @@ class Observer(Module, QParamsModuleMixin):
 
 
 class MinMaxObserver(Observer):
+    r"""
+    A Observer Module records input tensor's running min and max values to calc scale.
+
+    :param mode: set quantization mode.
+    :param eps: a initial maximum value to avoid division by zero problem.
+    :param dtype: a string indicating which dtype to collect scale and zero_point of.
+    """
+
     def __init__(
         self,
         mode: QuantMode = QuantMode.SYMMERTIC,
@@ -119,6 +128,14 @@ class MinMaxObserver(Observer):
 
 
 class SyncMinMaxObserver(MinMaxObserver):
+    r"""
+    A distributed version of :class:`~.MinMaxObserver`.
+
+    :param mode: set quantization mode.
+    :param eps: a initial maximum value to avoid division by zero problem.
+    :param dtype: a string indicating which dtype to collect scale and zero_point of.
+    """
+
     def forward(self, x_orig):
         if self.enable:
             x = x_orig.detach()
@@ -134,6 +151,15 @@ class SyncMinMaxObserver(MinMaxObserver):
 
 
 class ExponentialMovingAverageObserver(MinMaxObserver):
+    r"""
+    A :class:`~.MinMaxObserver` with momentum support for min/max updating.
+
+    :param momentum: momentum ratio for min/max updating.
+    :param mode: set quantization mode.
+    :param eps: a initial maximum value to avoid division by zero problem.
+    :param dtype: a string indicating which dtype to collect scale and zero_point of.
+    """
+
     def __init__(
         self,
         momentum: float = 0.9,
@@ -170,6 +196,15 @@ class ExponentialMovingAverageObserver(MinMaxObserver):
 
 
 class SyncExponentialMovingAverageObserver(ExponentialMovingAverageObserver):
+    r"""
+    A distributed version of :class:`~.ExponentialMovingAverageObserver`.
+
+    :param momentum: momentum ratio for min/max updating.
+    :param mode: set quantization mode.
+    :param eps: a initial maximum value to avoid division by zero problem.
+    :param dtype: a string indicating which dtype to collect scale and zero_point of.
+    """
+
     def forward(self, x_orig):
         if self.enabled:
             x = x_orig.detach()
@@ -192,6 +227,17 @@ class SyncExponentialMovingAverageObserver(ExponentialMovingAverageObserver):
 
 
 class HistogramObserver(MinMaxObserver):
+    r"""
+    A :class:`~.MinMaxObserver` using running histogram of tensor values
+    for min/max updating. Usually used for calibration quantization.
+
+    :param bins: number of bins to use for the histogram.
+    :param upsample_rate: which ratio to interpolate histograms in.
+    :param mode: set quantization mode.
+    :param eps: a initial maximum value to avoid division by zero problem.
+    :param dtype: a string indicating which dtype to collect scale and zero_point of.
+    """
+
     def __init__(
         self,
         bins: int = 2048,