The angular momentum flywheel subsystem of a Single Gimbal Control Moment Gyro(SGCMG) was designed to improve the attitude control accuray of satellites. Firstly, the impact of angular velocity fluctuations on the output torque of SGCMG was analyzed in theory. The conclusion suggests that when the expected speed is 5 000 r/min and the torque fluctuation is less than 0.002 Nm, the angular velocity fluctuations should be less than 5 r/min. Then, the angular momentum flywheel was driven by a Brushless Direct Current Motor(BLDCM), the control driver circuit was designed by a Field Programming Gate Array(FPGA),and an adaptive compensation PI control strategy was established to track the expected angular velocity. Test and experiments show that it takes 25 s to reach a steady-state from stillness to 5 000 r/min,the overshoot is less than 15 r/min and the steady-state accuracy is 2 r/min. Analysis of the data collected real-time by PC shows the rationality of the subsystem and indicates the angular moment wheel designed satisfies the requirement of the SGCMG, reduces the impact of angular velocity fluctuations on the output torque of SGCMG,and improves the platform control accuracy of satellites.