This paper presents a numerical study on control effectiveness of a high-speed underwater vehicle with cruciform stern configuration using a computational fluid dynamics approach. The calculation of the control derivatives of the underwater vehicle is validated by comparison with the experimental results of towing tank tests. The screw propeller of the vehicle is modeled as a momentum source and its influence on the computational results is examined. The numerical results show that the force derivatives of the vehicle are over-predicted by about 5% and the moment derivatives of the vehicle are over-predicted by about 10%.