An active composite variable damping rotational control device includes a variable damping module and a power module. The variable damping module includes a magnetorheological fluid tank and a rotational inertia wheel. The rotational inertia wheel is arranged in the magnetorheological fluid tank fully filled with magneorheological fluid. The power module includes a device tubular cavity, a driver, an encoder and a speed changer. The driver is fixed on the inner wall of the device tubular cavity. The driver, the encoder and the speed changer are coaxial. A driving shaft of the driver passes through the speed changer and extends into the magnetorheological fluid tank to be fixed perpendicularly at the center of the rotational inertia wheel. The control effect of the present invention may not be greatly affected by the change of a structural form and the change of an external load.