diff --git a/MdePkg/Include/Library/PeiServicesTablePointerLib.h b/MdePkg/Include/Library/PeiServicesTablePointerLib.h
index 6fb87949f3..1637e670d2 100644
--- a/MdePkg/Include/Library/PeiServicesTablePointerLib.h
+++ b/MdePkg/Include/Library/PeiServicesTablePointerLib.h
@@ -39,7 +39,7 @@ GetPeiServicesTablePointer (
 VOID
 EFIAPI
 SetPeiServicesTablePointer (
-  IN EFI_PEI_SERVICES ** PeiServicesTablePointer
+  IN CONST EFI_PEI_SERVICES ** PeiServicesTablePointer
   );
 
 #endif
diff --git a/MdePkg/Include/Uefi/UefiBaseType.h b/MdePkg/Include/Uefi/UefiBaseType.h
index 0d681a3a4d..fff78a80e5 100644
--- a/MdePkg/Include/Uefi/UefiBaseType.h
+++ b/MdePkg/Include/Uefi/UefiBaseType.h
@@ -48,8 +48,6 @@ typedef UINT64                    EFI_LBA;
 typedef UINT64                    EFI_PHYSICAL_ADDRESS;
 typedef UINT64                    EFI_VIRTUAL_ADDRESS;
 
-typedef UINT16                    STRING_REF;
-
 ///
 /// EFI Time Abstraction:
 ///  Year:       1998 - 20XX
diff --git a/MdePkg/Include/Uefi/UefiInternalFormRepresentation.h b/MdePkg/Include/Uefi/UefiInternalFormRepresentation.h
index 2364d11422..9c0f2a2f7d 100644
--- a/MdePkg/Include/Uefi/UefiInternalFormRepresentation.h
+++ b/MdePkg/Include/Uefi/UefiInternalFormRepresentation.h
@@ -23,8 +23,6 @@
 ///
 /// The following types are currently defined:
 ///
-typedef UINT32  RELOFST;
-
 typedef VOID*   EFI_HII_HANDLE;
 typedef CHAR16* EFI_STRING;
 typedef UINT16  EFI_IMAGE_ID;
diff --git a/MdePkg/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c b/MdePkg/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c
index 3dcbd2ae5a..fc045aeec0 100644
--- a/MdePkg/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c
+++ b/MdePkg/Library/PeiServicesTablePointerLib/PeiServicesTablePointer.c
@@ -19,7 +19,7 @@
 #include <Library/PeiServicesTablePointerLib.h>
 #include <Library/DebugLib.h>
 
-STATIC EFI_PEI_SERVICES  **gPeiServices;
+STATIC CONST EFI_PEI_SERVICES  **gPeiServices;
 
 /**
   The function cache the pointer of PEI services to global variable.
@@ -29,7 +29,7 @@ STATIC EFI_PEI_SERVICES  **gPeiServices;
 VOID
 EFIAPI
 SetPeiServicesTablePointer (
-  IN EFI_PEI_SERVICES  ** PeiServicesTablePointer
+  IN CONST EFI_PEI_SERVICES  ** PeiServicesTablePointer
   )
 {
   gPeiServices = PeiServicesTablePointer;
@@ -51,7 +51,7 @@ GetPeiServicesTablePointer (
   )
 {
   ASSERT (gPeiServices != NULL);
-  return (CONST EFI_PEI_SERVICES **) gPeiServices;
+  return gPeiServices;
 }
 
 
@@ -70,8 +70,8 @@ GetPeiServicesTablePointer (
 EFI_STATUS
 EFIAPI
 PeiServicesTablePointerLibConstructor (
-  IN EFI_PEI_FILE_HANDLE  FileHandle,
-  IN EFI_PEI_SERVICES     **PeiServices
+  IN EFI_PEI_FILE_HANDLE        FileHandle,
+  IN CONST EFI_PEI_SERVICES     **PeiServices
   )
 {
   gPeiServices = PeiServices;
diff --git a/MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointer.c b/MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointer.c
index bf331bc87e..11af09a040 100644
--- a/MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointer.c
+++ b/MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointer.c
@@ -65,7 +65,7 @@ GetPeiServicesTablePointer (
 VOID
 EFIAPI
 SetPeiServicesTablePointer (
-  IN EFI_PEI_SERVICES ** PeiServicesTablePointer
+  IN CONST EFI_PEI_SERVICES ** PeiServicesTablePointer
   )
 {
   IA32_DESCRIPTOR   Idtr;
diff --git a/MdePkg/Library/PeiServicesTablePointerLibKr7/PeiServicesTablePointer.c b/MdePkg/Library/PeiServicesTablePointerLibKr7/PeiServicesTablePointer.c
index 1c21263735..ebfec4be6c 100644
--- a/MdePkg/Library/PeiServicesTablePointerLibKr7/PeiServicesTablePointer.c
+++ b/MdePkg/Library/PeiServicesTablePointerLibKr7/PeiServicesTablePointer.c
@@ -48,7 +48,7 @@ GetPeiServicesTablePointer (
 VOID
 EFIAPI
 SetPeiServicesTablePointer (
-  IN EFI_PEI_SERVICES ** PeiServicesTablePointer
+  IN CONST EFI_PEI_SERVICES ** PeiServicesTablePointer
   )
 {
   AsmWriteKr7 ((UINT64)(UINTN)PeiServicesTablePointer);