The performance of GaN-based Schottky device was simulated numerically based on a two-dimensional model,which focused on the effect of interface layer and bulk layer to electric characteristics,i.e.distribution of strength of electric field and current-voltage characteristic of different MIS Schottky devices.The results indicated that the interface layer mainly affects the current characteristic of device and turn-on voltage，improves the strength of electric field and reduces the dark current,and the bulk layer mainly affects the distribution of electric field and the forward current of device.We can optimize the fabric and improve the performance of devices.