In VSP forward modeling with the wave field extrapolation method, we can just simulate upward wave or simulate upward wave and downward wave simultaneously according to the situation, and the multiple wave can be controlled efficiently. In general, under the condition of being only concerned with the primary reflection, we needn't simulate the multiple wave. This method has high efficiency compared with other wave equation modeling methods. In this paper, the split-step Fourier method was used to extrapolate the wave field, which can guarantee the stability of wave extrapolation and the modeling accuracy for the complex model. Model test shows that this method can simulate VSP efficiently and the modeling result is correct and reliable.