The numerical model of integrative internal and external flow field of underwater vehicle equipped with a pump-jet propulsor was established. The computational region discretization was conducted  by using high quality multiblock structure grid. The steady hydrodynamic performance was calculated by adopting Reynolds time averaged method, SST k-ω turbulence model and finite volume method. The open water performance curve was given, indicating that the pump-jet propulsor had a high efficiency and ideal balance of performance. Pressure distributions along the meridian of vehicle hull and at various heights of blade were analyzed. The tip vortex of the rotor was displayed and explained. The velocity components were discussed in the location before the rotor, in the middle of the gap and behind the stator. The comparison with the results of the full stage model showed that the single stage model was applicable and feasible for the research.