The strap-down inertial navigation system with rotation-modulation has raised a higher requirement for the precision of position transformation system; and aiming at this requirement and based on the DC (direct current) torque motor, a position transformation system and a control method are proposed. The revolving transformer to measure the angle and the DC torque motor to drive the position transformation system are used to study the position-velocity-current PID (proportion integration differentiation) control loop. The feed-forward control method and saturation correction algorithm are proposed to realize the high accuracy of the position control for the transformation system. The Simulink numerical simulation results show that the control method is effective and the control precision can satisfy the design specification requirement. Under actual test conditions, the field-test results show that the method is practicable; the adaptability for the environment and the control precision can meet the design requirements.