Abstract: Recently, the control moment gyroscopes have been widely used in spacecraft attitude control. In order to reduce the influence of the vibration caused by the highspeed momentum wheel, a vibration isolation device is introduced. However, vibration isolating device has an effect on the dynamic characteristics of the internal mechanism of the control torque gyroscope. This paper establishes a dynamic model of the control moment gyroscope with the influence of the flexible vibration isolation mechanism. The kinematic relationship is established by Euler angle transformation, and the dynamic characteristics are established by using the energy method. Numerical simulation and analysis are carried out in Matlab. It is found that the vibration isolation structure has an influence on the output torque of the gyroscope. The gyro moment under the flexible support has obvious fluctuation, and the fluctuation range increases with the increase of the rotational speed of the momentum wheel. At the same time, the flexible vibration isolation mechanism also generates the disturbance torque, which has a great influence on the control of the frame motor.