diff --git a/torch/quantization/fuse_modules.py b/torch/quantization/fuse_modules.py
index d8f06e538726..e6669519b964 100644
--- a/torch/quantization/fuse_modules.py
+++ b/torch/quantization/fuse_modules.py
@@ -28,7 +28,7 @@ def _set_module(model, submodule_key, module):
 
     setattr(cur_mod, tokens[-1], module)
 
-def fuse_known_modules(mod_list):
+def fuse_known_modules(mod_list, additional_fuser_method_mapping=None):
     r"""Returns a list of modules that fuses the operations specified
      in the input module list.
 
@@ -41,7 +41,7 @@ def fuse_known_modules(mod_list):
     the fused operation. The rest of the elements are set to nn.Identity()
     """
     types = tuple(type(m) for m in mod_list)
-    fuser_method = get_fuser_method(types)
+    fuser_method = get_fuser_method(types, additional_fuser_method_mapping)
     if fuser_method is None:
         raise NotImplementedError("Cannot fuse modules: {}".format(types))
     new_mod : List[Optional[nn.Module]] = [None] * len(mod_list)
@@ -64,20 +64,23 @@ def fuse_known_modules(mod_list):
 
     return new_mod
 
-def _fuse_modules(model, modules_to_fuse, fuser_func=fuse_known_modules):
-
+# TODO: remove fuser_func?
+def _fuse_modules(model, modules_to_fuse, fuser_func=fuse_known_modules, fuse_custom_config_dict=None):
+    if fuse_custom_config_dict is None:
+        fuse_custom_config_dict = {}
+    additional_fuser_method_mapping = fuse_custom_config_dict.get("additional_fuser_method_mapping", {})
     mod_list = []
     for item in modules_to_fuse:
         mod_list.append(_get_module(model, item))
 
     # Fuse list of modules
-    new_mod_list = fuser_func(mod_list)
+    new_mod_list = fuser_func(mod_list, additional_fuser_method_mapping)
 
     # Replace original module list with fused module list
     for i, item in enumerate(modules_to_fuse):
         _set_module(model, item, new_mod_list[i])
 
-def fuse_modules(model, modules_to_fuse, inplace=False, fuser_func=fuse_known_modules):
+def fuse_modules(model, modules_to_fuse, inplace=False, fuser_func=fuse_known_modules, fuse_custom_config_dict=None):
     r"""Fuses a list of modules into a single module
 
     Fuses only the following sequence of modules:
@@ -101,6 +104,14 @@ def fuse_modules(model, modules_to_fuse, inplace=False, fuser_func=fuse_known_mo
                     of the same length. For example,
                     fuser_func([convModule, BNModule]) returns the list [ConvBNModule, nn.Identity()]
                     Defaults to torch.quantization.fuse_known_modules
+        `fuse_custom_config_dict`: custom configuration for fusion:
+         Example:
+         fuse_custom_config_dict = {
+           # Additional fuser_method mapping
+           "additional_fuser_method_mapping": {
+              (torch.nn.Conv2d, torch.nn.BatchNorm2d): fuse_conv_bn
+           },
+         }
     Returns:
         model with fused modules. A new copy is created if inplace=True.
 
@@ -124,9 +135,9 @@ def fuse_modules(model, modules_to_fuse, inplace=False, fuser_func=fuse_known_mo
 
     if all(isinstance(module_element, str) for module_element in modules_to_fuse):
         # Handle case of modules_to_fuse being a list
-        _fuse_modules(model, modules_to_fuse, fuser_func)
+        _fuse_modules(model, modules_to_fuse, fuser_func, fuse_custom_config_dict)
     else:
         # Handle case of modules_to_fuse being a list of lists
         for module_list in modules_to_fuse:
-            _fuse_modules(model, module_list, fuser_func)
+            _fuse_modules(model, module_list, fuser_func, fuse_custom_config_dict)
     return model
diff --git a/torch/quantization/quantize.py b/torch/quantization/quantize.py
index 82295e72d5e5..9aa52d373ff6 100644
--- a/torch/quantization/quantize.py
+++ b/torch/quantization/quantize.py
@@ -212,6 +212,7 @@ def prepare(model, inplace=False, allow_list=None,
     if not inplace:
         model = copy.deepcopy(model)
 
+    # TODO: remove allow_list
     qconfig_propagation_list = allow_list
     if qconfig_propagation_list is None:
         qconfig_propagation_list = get_default_qconfig_propagation_list()
@@ -365,6 +366,7 @@ def prepare_qat(model, mapping=None, inplace=False):
     torch._C._log_api_usage_once("quantization_api.quantize.prepare_qat")
     if mapping is None:
         mapping = get_default_qat_module_mappings()
+
     if not inplace:
         model = copy.deepcopy(model)
 
diff --git a/torch/quantization/quantize_fx.py b/torch/quantization/quantize_fx.py
index 3f869b3714f5..37fec5b117e8 100644
--- a/torch/quantization/quantize_fx.py
+++ b/torch/quantization/quantize_fx.py
@@ -177,12 +177,12 @@ def prepare_fx(model, qconfig_dict, inplace=False, prepare_custom_config_dict=No
 
         # Additional fuser_method mapping
         "additional_fuser_method_mapping": {
-           (ModuleClass1, ModuleClass2): fuse_module1_module2
+           (torch.nn.Conv2d, torch.nn.BatchNorm2d): fuse_conv_bn
         },
 
         # Additioanl module mapping for qat
         "additional_qat_module_mapping": {
-           FloatModule: QATModule
+           torch.nn.intrinsic.ConvBn2d: torch.nn.qat.ConvBn2d
         },
 
         # Additional fusion patterns