As one of the key steps in seismic data processing, stacking can effectively suppress the noise and improve signal-to-noise ratio. In VSP seismic exploration, the imaging precision of the conventional superposition method is greatly limited in the complex structure. In this paper, the authors used the Gaussian beam method as forward modeling method for complex structure, compared the wave field characteristics of model with features of real data, and obtained the appropriate velocity field through adjusting the parameters. The idea of inverse Gaussian beam was adopted in the process of stacking, the common reflection point gathers were obtained by migrating the reflection wave field of real seismic data to the correct position, and then the stacking field characteristics could be acquired by stacking the data in an appropriate bin size. A large number of model tests show that VSP Gaussian beam stacking method can effectively invert the underground structure characteristics. The method was used in the imaging study of M area, and the results show that this method can accurately invert the underground structure characteristics and provide an accurate basis for seismic data processing and interpretation.