To　ensure　a　high　reverse　breakdown　voltage　at　a　small　size　and　improve　the　uniform　electric　field　of　the　terminal　structure　of　the　device.　This　paper　is　based　on　simulation　calculations　to　optimize　the　vertical　power　devices.　Establish　a　model　of　GaN　vertical　SBD,　N-GaN　drift　layer　thickness　is　4μm-5μm,　the　doping　concentration　is　1.5×1016cm-3.　N+GaN　the　doping　concentration　of　the　current　extension　layer　is　1019cm-3.　Under　the　premise　of　determining　the　thickness　of　the　current　expansion　layer　as　5μm,　this　paper　sets　the　thickness　of　current　expansion　layer　(Ln+gan1)　as　0.1μmsets　the　thickness　of　N+GaN　(Ln+gan)　as　0.6μm.　Then　sets　Lac1　and　Lac2　optimized　as　10μm　and　5μm.　The　on-resistance　of　the　optimized　quasi-vertical　SBD　reduce　from　0.93　mΩ•cm2　to　0.55　mΩ•cm2,　breakdown　voltage　increase　from　530V　to　560V.　Secondly　this　paper　optimized　the　terminal　structure　of　the　device,　determine　the　passivation　layer　thickness　as　0.4μm,　the　length　of　field　plate　is　8μm.　Finally,　the　influence　of　the　two　terminal　structures　on　the　device　is　compared,　the　field　plate　has　no　effect　on　the　forward　characteristics　of　the　device.　After　optimization,　the　on-resistance　is　0.565mΩ•cm2,　increases　the　breakdown　voltage　of　the　device　to　632V.　　©　2023　IEEE.