The behavior of Fokker-Planck Equation for a stochastic resonance problem is studied by using finite difference schemes. The numerical results coincide with the analytical approximate theory under the conditions of adiabatic approximation ω?D?△V and small signal approximation A?1. Although the system rexhibits evidently deterministic non-linear vibration properties when the amplitude of periodic driving force is large, the adiabatic approximate analytical theory can cover the principal properties of stochastic resonance which occurs in the bistable system.