The invention provides an ISG (integrated starter generator) motor. The ISG motor comprises a shell, a stator, a rotor, a rotating shaft, two bearings, a front end cover and a rear end cover. The ISG motor is a disc-type motor, the rotating shaft is a hollow shaft, and the disc-type motor also comprises a separation plate, a ball-cage constant-speed coupler and a rotary transformer. The invention also provides a hybrid power drive system with the ISG motor. The hybrid power drive system comprises an engine, a car clutch, a drive motor, a transmission shaft driving axle and a control assembly, the engine is sequentially connected with the car clutch, the drive motor and the transmission shaft driving axle, the engine is coaxially and integrally installed with the car clutch and the drive motor, the ISG motor is connected with the engine by virtue of the ball-cage constant-speed coupler, and the ISG motor and the engine are coaxially installed in a splitting manner. The ISG motor is small in size, small in occupied installation space and small in weight, an additional set of flywheel and flywheel shell is not needed, the axial length is reduced, and the problems caused by the arrangement of a belt transmission device such as low transmission efficiency, high oil consumption and complicated structure of the drive system can be avoided.