An active control system for a rolling behavior of a high-speed train, comprising: a sensor adapted to be arranged on the train; a controller; and an output device ; wherein the output device can be arranged on a joint between two adjacent carriages of the train; the output device comprises a power unit , an output unit and a casing ; and the power unit and the output unit are provided inside the casing ; the casing comprises a bottom plate , an annular side plate and a cover plate ; the casing is further provided with a through hole which penetrates through the bottom plate and the cover plate ; and the bottom plate and the cover plate can be arranged on the two adjacent carriages, respectively; the power unit comprises a motor and a speed-increasing gear set ; the speed-increasing gear set comprises a main speed-increasing gear and a secondary speed-increasing gear ; the motor is fixed on the bottom plate ; the main speed-increasing gear is arranged on the motor and the secondary speed-increasing gear is fixed on the bottom plate ; the main speed-increasing gear engages with the secondary speed-increasing gear ; and the sensor and the motor are electrically connected to the controller, respectively; and the output unit comprises a rotation inertia ring , a torque transmission ring and a connecting ring which are all hollow circular rings; and the rotation inertia ring , the torque transmission ring and the connecting ring are coaxial with the through hole ; the connecting ring is fixed on the bottom plate ; the torque transmission ring is connected between the rotation inertia ring and the connecting ring ; an outer circumference of the rotation inertia ring is provided with teeth; and the rotation inertia ring engages with the secondary speed-increasing gear through the teeth. a sensor adapted to be arranged on the train; a controller; and an output device ; wherein the output device can be arranged on a joint between two adjacent carriages of the train; the output device comprises a power unit , an output unit and a casing ; and the power unit and the output unit are provided inside the casing ; the casing comprises a bottom plate , an annular side plate and a cover plate ; the casing is further provided with a through hole which penetrates through the bottom plate and the cover plate ; and the bottom plate and the cover plate can be arranged on the two adjacent carriages, respectively; the power unit comprises a motor and a speed-increasing gear set ; the speed-increasing gear set comprises a main speed-increasing gear and a secondary speed-increasing gear ; the motor is fixed on the bottom plate ; the main speed-increasing gear is arranged on the motor and the secondary speed-increasing gear is fixed on the bottom plate ; the main speed-increasing gear engages with the secondary speed-increasing gear ; and the sensor and the motor are electrically connected to the controller, respectively; and the output unit comprises a rotation inertia ring , a torque transmission ring and a connecting ring which are all hollow circular rings; and the rotation inertia ring , the torque transmission ring and the connecting ring are coaxial with the through hole ; the connecting ring is fixed on the bottom plate ; the torque transmission ring is connected between the rotation inertia ring and the connecting ring ; an outer circumference of the rotation inertia ring is provided with teeth; and the rotation inertia ring engages with the secondary speed-increasing gear through the teeth. <EOS>