Background　based　coding　is　an　effective　scheme　to　improve　the　coding　efficiency　of　surveillance　videos.　However,　it　takes　a　long　time　to　generate　a　high　quality　background　picture　(BG-picture).　And　the　encoding　of　the　high　quality　BG-picture　will　increase　the　bitrate　abruptly.　To　solve　these　problems,　a　progressive　background　updating　based　coding　scheme　is　proposed　in　this　paper.　In　the　proposed　scheme,　the　BG-picture　is　updated　block　by　block.　To　improve　the　overall　coding　efficiency,　an　importance　map　is　designed　to　select　the　valid　background　blocks　(B-blocks)　progressively　which　will　be　encoded　with　high　quality.　It　is　worth　noting　that　only　the　valid　B-blocks　is　encoded　instead　of　the　entire　BG-picture.　Compared　with　the　reference　software　of　Versatile　Video　Coding　(VVC),　the　proposed　scheme　achieves　about　23.3　percent　bit-rate　saving　on　average.　©　2019　IEEE.