In　order　to　improve　the　performance　of　GaN-based　quasivertical　MIS　SBD,　this　paper　proposes　and　designs　a　new　MIS　SBD　with　MIS　(metal-insulation-semiconductor)　terminal　structure,　and　optimizes　its　structural　parameters　via　simulation.　The　characteristic　simulation　result　shows　that　the　on-resistance　of　conventional　quasi-vertical　SBD　and　new　quasi-vertical　MIS　SBD　are　0.565m　Omega　center　dot　cm(2)　and　0.556m　Omega　center　dot　cm(2)　respectively.　And　the　breakdown　voltage　is　increased　from　632V　to　1056V.　After　optimization,　including　the　length　and　thickness　of　the　insulation　dielectric　layer　and　the　thickness　of　N-GaN　layer,　the　on-resistance　of　quasi-vertical　MIS　SBD　increases　slightly　to　0.648m　Omega　center　dot　cm(2),　but　the　breakdown　voltage　reaches　1624V.　Besides,　the　new　structure　can　effectively　alleviate　the　current　crowding　phenomenon,　alleviate　the　peak　electric　field　at　the　edge　of　the　anode　in　reverse　bias,　and　make　the　electric　field　distribution　in　the　device　more　uniform.