diff --git a/EmulatorPkg/EmulatorPkg.dsc b/EmulatorPkg/EmulatorPkg.dsc
index 20f1187713..109685b062 100644
--- a/EmulatorPkg/EmulatorPkg.dsc
+++ b/EmulatorPkg/EmulatorPkg.dsc
@@ -237,9 +237,11 @@
 
 [Components]
 !if "IA32" in $(ARCH) || "X64" in $(ARCH)
-  !if "MSFT" in $(FAMILY)
+  !if "MSFT" in $(FAMILY) || $(WIN_HOST_BUILD) == TRUE
     ##
     #  Emulator, OS WIN application
+    #  CLANG9 is cross OS tool chain. It depends on WIN_HOST_BUILD flag
+    #  to build WinHost application.
     ##
     EmulatorPkg/Win/Host/WinHost.inf
   !else
@@ -419,7 +421,17 @@
 
   MSFT:DEBUG_*_*_CC_FLAGS = /Od /Oy-
   MSFT:NOOPT_*_*_CC_FLAGS = /Od /Oy-
+  GCC:DEBUG_CLANG9_*_CC_FLAGS =-O0 -Wno-unused-command-line-argument -Wno-incompatible-pointer-types -Wno-enum-conversion -Wno-incompatible-pointer-types -Wno-sometimes-uninitialized -Wno-constant-conversion -Wno-main-return-type
 
   MSFT:*_*_*_DLINK_FLAGS     = /ALIGN:4096 /FILEALIGN:4096 /SUBSYSTEM:CONSOLE
   MSFT:DEBUG_*_*_DLINK_FLAGS = /EXPORT:InitializeDriver=$(IMAGE_ENTRY_POINT) /BASE:0x10000
   MSFT:NOOPT_*_*_DLINK_FLAGS = /EXPORT:InitializeDriver=$(IMAGE_ENTRY_POINT) /BASE:0x10000
+
+!if $(WIN_HOST_BUILD) == TRUE
+  #
+  # CLANG9 tool chain depends on WIN_HOST_BUILD flag to generate the windows application.
+  #
+  GCC:*_CLANG9_*_DLINK_FLAGS     = /ALIGN:4096 /FILEALIGN:4096 /SUBSYSTEM:CONSOLE
+  GCC:DEBUG_CLANG9_*_DLINK_FLAGS = /EXPORT:InitializeDriver=$(IMAGE_ENTRY_POINT) /BASE:0x10000
+  GCC:NOOPT_CLANG9_*_DLINK_FLAGS = /EXPORT:InitializeDriver=$(IMAGE_ENTRY_POINT) /BASE:0x10000
+!endif
diff --git a/EmulatorPkg/Win/Host/WinHost.c b/EmulatorPkg/Win/Host/WinHost.c
index 9aba3c8959..62a89f7617 100644
--- a/EmulatorPkg/Win/Host/WinHost.c
+++ b/EmulatorPkg/Win/Host/WinHost.c
@@ -356,7 +356,7 @@ Returns:
 INTN
 EFIAPI
 main (
-  IN  INTN  Argc,
+  IN  INT  Argc,
   IN  CHAR8 **Argv,
   IN  CHAR8 **Envp
   )
@@ -391,8 +391,8 @@ Returns:
   VOID                  *SecFile;
   CHAR16                *MemorySizeStr;
   CHAR16                *FirmwareVolumesStr;
-  UINT32                ProcessAffinityMask;
-  UINT32                SystemAffinityMask;
+  UINTN                 ProcessAffinityMask;
+  UINTN                 SystemAffinityMask;
   INT32                 LowBit;
 
   //
@@ -414,7 +414,7 @@ Returns:
   // Determine the first thread available to this process.
   //
   if (GetProcessAffinityMask (GetCurrentProcess (), &ProcessAffinityMask, &SystemAffinityMask)) {
-    LowBit = (INT32)LowBitSet32 (ProcessAffinityMask);
+    LowBit = (INT32)LowBitSet32 ((UINT32)ProcessAffinityMask);
     if (LowBit != -1) {
       //
       // Force the system to bind the process to a single thread to work
diff --git a/EmulatorPkg/Win/Host/WinHost.inf b/EmulatorPkg/Win/Host/WinHost.inf
index 631d5a6470..1adca10d79 100644
--- a/EmulatorPkg/Win/Host/WinHost.inf
+++ b/EmulatorPkg/Win/Host/WinHost.inf
@@ -95,3 +95,9 @@
   MSFT:*_VS2017_X64_DLINK_FLAGS      = /LIBPATH:"%VCToolsInstallDir%lib\x64" /LIBPATH:"%UniversalCRTSdkDir%lib\%UCRTVersion%\ucrt\x64" /LIBPATH:"%WindowsSdkDir%lib\%WindowsSDKLibVersion%\um\x64" /NOLOGO /SUBSYSTEM:CONSOLE /NODEFAULTLIB /IGNORE:4086 /MAP /OPT:REF /DEBUG /MACHINE:AMD64 /LTCG Kernel32.lib MSVCRTD.lib vcruntimed.lib ucrtd.lib Gdi32.lib User32.lib Winmm.lib Advapi32.lib
   MSFT:*_*_X64_ASM_FLAGS            == /nologo /W3 /WX /c /Cx /Zd /W0 /Zi
   MSFT:*_*_X64_ASMLINK_FLAGS        == /link /nologo
+
+  GCC:*_CLANG9_X64_DLINK_FLAGS == /out:"$(BIN_DIR)\$(BASE_NAME).exe" /base:0x10000000 /pdb:"$(BIN_DIR)\$(BASE_NAME).pdb"  /LIBPATH:"%UniversalCRTSdkDir%lib\%UCRTVersion%\ucrt\x64" /LIBPATH:"%WindowsSdkDir%lib\%WindowsSDKLibVersion%\um\x64" /LIBPATH:"%VCToolsInstallDir%lib\x64"   /NOLOGO /SUBSYSTEM:CONSOLE /NODEFAULTLIB /IGNORE:4086  /OPT:REF /DEBUG /MACHINE:AMD64 Kernel32.lib MSVCRTD.lib vcruntimed.lib ucrtd.lib Gdi32.lib User32.lib Winmm.lib Advapi32.lib /lldmap  /EXPORT:InitializeDriver=_ModuleEntryPoint
+  GCC:*_CLANG9_X64_CC_FLAGS == -m64 -g -fshort-wchar -fno-strict-aliasing -Wall -c -include AutoGen.h -D _CRT_SECURE_NO_WARNINGS -Wnonportable-include-path  -D UNICODE -D _CRT_SECURE_NO_DEPRECATE
+
+  GCC:*_CLANG9_IA32_DLINK_FLAGS == /out:"$(BIN_DIR)\$(BASE_NAME).exe" /base:0x10000000 /pdb:"$(BIN_DIR)\$(BASE_NAME).pdb" /LIBPATH:"%UniversalCRTSdkDir%lib\%UCRTVersion%\ucrt\x86" /LIBPATH:"%WindowsSdkDir%lib\%WindowsSDKLibVersion%\um\x86" /LIBPATH:"%VCToolsInstallDir%ib\x86"   /NOLOGO /SUBSYSTEM:CONSOLE /NODEFAULTLIB /IGNORE:4086  /OPT:REF /DEBUG /MACHINE:I386 Kernel32.lib MSVCRTD.lib vcruntimed.lib ucrtd.lib Gdi32.lib User32.lib Winmm.lib Advapi32.lib /lldmap  /EXPORT:InitializeDriver=_ModuleEntryPoint
+  GCC:*_CLANG9_IA32_CC_FLAGS == -m32 -g -fshort-wchar -fno-strict-aliasing -Wall -c -include AutoGen.h -D _CRT_SECURE_NO_WARNINGS -Wnonportable-include-path  -D UNICODE -D _CRT_SECURE_NO_DEPRECATE