diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 9c521ae8c6..addad6dd9a 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -109,6 +109,10 @@
 [PcdsFeatureFlag.common]
   gEfiMdeModulePkgTokenSpaceGuid.PcdSupportUpdateCapsuleRest|FALSE|BOOLEAN|0x0001001d
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiPcdDatabaseTraverseEnabled|TRUE|BOOLEAN|0x00010020
+  ## If PcdDxePcdDatabaseTraverseEnabled is TRUE, PCD_PROTOCOL.GetNextToken can 
+  #  get next PCD entry from PCD database, If FALSE, PCD_PROTOCOL.GetNextToken 
+  #  return EFI_SUPPORTED.
+  #
   gEfiMdeModulePkgTokenSpaceGuid.PcdDxePcdDatabaseTraverseEnabled|TRUE|BOOLEAN|0x00010021
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiPcdDatabaseSetEnabled|TRUE|BOOLEAN|0x00010030
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiPcdDatabaseGetSizeEnabled|TRUE|BOOLEAN|0x00010031
@@ -126,8 +130,15 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdUnicodeCollation2Support|TRUE|BOOLEAN|0x00010041
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE|BOOLEAN|0x00010042
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|TRUE|BOOLEAN|0x00010043
+  ## If PcdPeiCoreImageLoaderSearchTeSectionFirst is TRUE, PeiCore will search TE section
+  #  firstly when loading an PEIM image, If FALSE, PeiCore will search PE section firstly.
+  #
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreImageLoaderSearchTeSectionFirst|TRUE|BOOLEAN|0x00010044
+  ## If PcdSupportHardwareErrorRecord is TRUE, support hardware error record via variable.
+  #  If FALSE, does not support.
   gEfiMdeModulePkgTokenSpaceGuid.PcdSupportHardwareErrorRecord|FALSE|BOOLEAN|0x00010045
+  ## If PcdUgaConsumeSupport is TRUE, EFI_UGA_DRAW_PROTOCOL is produced by platform.
+  #  Otherwice, EFI_UGA_DRAW_PROTOCOL is not produced by platform.
   gEfiMdeModulePkgTokenSpaceGuid.PcdUgaConsumeSupport|TRUE|BOOLEAN|0x00010046
   gEfiMdeModulePkgTokenSpaceGuid.PcdTurnOffUsbLegacySupport|FALSE|BOOLEAN|0x00010047
 
@@ -139,14 +150,24 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdSupportFullConfigRoutingProtocol|TRUE|BOOLEAN|0x00010202
 
 [PcdsFixedAtBuild.common]
+  ## Dynamic type PCD can be registered callback function for Pcd setting action.
+  #  PcdMaxPeiPcdCallBackNumberPerPcdEntry indicate maximum number of callback function
+  #  for a dynamic PCD used in PEI phase.
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxPeiPcdCallBackNumberPerPcdEntry|0x08|UINT32|0x0001000f
+  ## VPD type PCD allow developer point an absoluted physical address PcdVpdBaseAddress
+  #  to store PCD value. 
+  #
   gEfiMdeModulePkgTokenSpaceGuid.PcdVpdBaseAddress|0x0|UINT32|0x00010010
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxSizePopulateCapsule|0x6400000|UINT32|0x0001001e
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxSizeNonPopulateCapsule|0xa00000|UINT32|0x0001001f
   gEfiMdeModulePkgTokenSpaceGuid.PcdMaxPeiPerformanceLogEntries|40|UINT8|0x0001002f
+  ## Maximum number of FV is supported by PeiCore's dispatching.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxFvSupported|6|UINT32|0x00010030
+  ## Maximum PEIM count in every FV is supported by PeiCore's dispatching.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxPeimPerFv|32|UINT32|0x00010031
+  ## Maximum stack size for PeiCore.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxPeiStackSize|0x20000|UINT32|0x00010032
+  ## Maximum PPI count is supported by PeiCore's PPI database.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPeiCoreMaxPpiSupported|64|UINT32|0x00010033
   gEfiMdeModulePkgTokenSpaceGuid.PcdRealTimeClockUpdateTimeout|100000|UINT32|0x00010034
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase|0x0|UINT32|0x30000001
@@ -158,7 +179,10 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize|0x0|UINT32|0x30000014
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingBase|0x0|UINT32|0x30000010
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize|0x0|UINT32|0x30000011
+  ## Default timeout value for displaying progressing bar in before boot OS.
+  #  This value can be changed in BDS.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPlatformBootTimeOutDefault|10|UINT16|0x40000001
+  ## error level for hardware recorder.
   gEfiMdeModulePkgTokenSpaceGuid.PcdHardwareErrorRecordLevel|1|UINT16|0x40000002
 
 [PcdsFixedAtBuild.IA32]