In this paper, Silvaco TCAD was used to establish the model to simulate the optical and electrical properties of graphene, and the experimental bipolar curves of graphene with different doping degrees were calculated. Furthermore, modeling and simulation of graphene-silicon photoconductive photodetector based on top gate regulation were carried out. The simulation results show that the top gate voltage can change the built-in potential of graphene-silicon heterojunction by regulating the type and concentration of graphene carriers, so as to improve the gain of graphene-silicon photodetector. Then the gate-controlled graphene-silicon photodetector was prepared and it is consistent with the gain enhancement of the graphene-silicon photoconductive photodetectors fabricated at 1550nm band.