The　process　of　AZ31　sheet　with　a　thickness　of　1.2　mm　and　diameter　of　52　mm　being　pressed　into　a　dish　with　29mm　diameter　was　simulated　by　FEM.　The　die　parameters　were　optimized　through　analyzing　its　influence　on　the　maximum　principal　stress　and　corresponding　experiments　were　carried　out.　The　simulation　results　show　that　the　optimization　of　the　die　gap　and　the　round　radius　of　dent　die　and　punch　could　decrease　the　value　of　the　maximum　principal　stress,　decelerate　the　forming　of　crevice　and　improve　the　deformation　property　of　magnesium　alloy.　The　appropriate　parameters　derived　are:　the　round　radius　of　dent　die　2.6　mm,　the　round　radius　of　punch　1.8　mm　and　the　half　gap　1.3　mm.　The　analyzing　results　were　validated　by　experiments.