Ag ₂ZnSnSe ₄is an n-type semiconductor with a suitable bandgap of 1.4 eV. In the present study, a graphene/Ag ₂ZnSnSe ₄induced p-n junction thin film solar cell is proposed and the physical mechanism and performance influencing factors of the solar cell are simulated and analyzed by using the wxAMPS software. The simulation results show that when a high work function graphene contacts an n-type Ag ₂ZnSnSe ₄semiconductor, the energy band of the Ag ₂ZnSnSe ₄absorber layer bends upward, meanwhile a p-type Ag ₂ZnSnSe ₄inversion layer is induced on the surface of n-type Ag ₂ZnSnSe ₄, therefore the p-type Ag ₂ZnSnSe ₄and n-type Ag ₂ZnSnSe ₄form an induced p-n homojunction. It is found that the work function of graphene and back contact significantly influence the photogenerated carrier separation, transportation and collection. The graphene work function should be 5.5 eV and the work function of back contact should not be greater than 4.4 eV, which is beneficial to the improving of the device performance. The doping concentration of Ag ₂ZnSnSe ₄absorber mainly affects the short-circuit current of the device, however, the defect density of Ag ₂ZnSnSe ₄absorber affects the whole device performance. When the work function of graphene and back contact are 5.5 eV and 3.8 eV, the doping concentration and defect density of Ag ₂ZnSnSe ₄absorber are 10 ¹⁶cm ^–3and 10 ¹⁴cm ^–33, respectively, the conversion efficiency of the graphene/Ag ₂ZnSnSe ₄induced p-n junction thin film solar cell can reach 23.42%. These simulation results provide the idea and physical explanation for designing a novel type of solar cell with high efficiency and low cost.