In order to optimize the walkaround VSP (W-VSP) field acquisition plan and solve the problem of fine structure imaging around the well, the three-dimensional (3D) Gaussian beam forward method is used to conduct trial calculations and analysis on the W-VSP geometry system, and the forward wave field is used to guide W-VSP wavefield separation work, it provides a data basis for VSP imaging. Firstly, the receiver point plane is built through the location of geophone by referring the idea of Gaussian beam ray tracing for ground seismic. Secondly, the effective rays are selected and the dynamic ray tracing is completed by judging whether the distance between the ray reaching the receiver point plane and the receiver point satisfy the effective half width of Gaussian beam. Finally, the forward simulation results are used to guide VSP field geometry system design and wave field separation. The theoretical model and the trial calculation of actual data show that the Gaussian beam forward modeling method can accurately simulate the propagation characteristics of 3D W-VSP wave field, guide the design of W-VSP field geometry system, and provide a theoretical basis for the wave field separation of VSP field data.