The invention provides a hybrid power drive system, and belongs to the technical field of machinery. The problem that an existing hybrid power drive system is complex in structure, large in size and low in drive accuracy is solved. The hybrid power drive system includes an engine, a driving motor, an output shaft, a generator and a differential mechanism; an input shaft of the driving motor is provided with a first driving gear, the two ends of the output shaft are correspondingly provided with a first intermediate gear and a second intermediate gear, the first driving gear is meshed with the first intermediate gear, the second intermediate gear is connected with the differential mechanism in a drive mode, the engine, the generator and the driving motor are successively arranged in a coaxial mode, a rotating shaft of the engine penetrates into a rotor of the generator and is connected with the rotor of the generator in a drive mode, the rotating shaft of the engine is connected with a second driving gear through a clutch, and the second driving gear is meshed with the second intermediate gear. According to the hybrid power drive system, the radial and axial sizes are reduced, the structure is simplified, the manufacturing cost is lowered, the driving accuracy is improved, and the NVH performance and carrying of a whole vehicle are improved.