The　aim　of　this　research　is　to　analyze　the　influence　of　shrinkage　behavior　on　the　deformation　of　forming　parts　in　mask　projection　stereolithography.　A　mask　projection　stereolithography　machine　based　on　DLP　(digital　light　procession)　technology　was　designed,　and　the　shrinkage　of　photosensitive　resin　during　light-cured　process　was　analyzed.　The　shrinkage　behavior　of　resin　in　different　exposure　situations,　free-surface　and　constrain-surface,　and　also　in　secondary　curing　process　was　studied.　The　result　shows　that　in　free-surface,　the　shrinkage　of　B5B　type　resin　is　proportional　to　the　exposure　time,　eventually　it　stabilizes　at　around　4%.　When　it　is　in　constrain-surface,　the　overflowed　light　curing　effect　leads　to　shrinkage　which　decreases　with　exposure　time　increased,　and　the　shrinkage　generated　in　the　secondary　curing　process　accounts　for　40%~50%　of　total.　©　2015,　Beijing　University　of　Technology.　All　right　reserved.