In order to study the characteristics of fluid field of certain type launch vehicle, the numerical simulation of the flow field of a launch vehicle under 5 m workstation was conducted with CFD(Computational Fluid Dynamics) technique. Based on the 3D single nozzle engine model, with the standard k-e turbulence model, the mixed gas flow was considered, and then, the flow field of engine tail flame was obtained, the change of the plume wave structure with time was analyzed. The results showed that the parameters of the flow field and the structure of the shock wave system are consistent with the theoretical analysis results, which provide a reference and theoretical basis for the subsequent experimental measurements.