The invention discloses a hybrid system of a four-wheel-drive hybrid vehicle, which comprises an engine and a front axle transmission gear connected with the engine. The engine is connected with a generator by a first clutch, the generator is connected with a vehicular energy storage device, and the vehicular energy storage device is connected with a rear axle driving motor. An intermediate transmission of a traditional four-wheel-drive vehicle is omitted, the hybrid system is simple in structure, convenient in control and low in cost, and an integrated design and system matching are easy to be realized. Simultaneously, torque of front wheels and rear wheels of the integral vehicle can be analyzed, calculated and distributed by an integral vehicle controller according to a running state of the integral vehicle, higher driving flexibility is realized, accordingly, the hybrid system can meet the requirement on a four-wheel-drive function of the hybrid vehicle, and purposes of energy conservation and emission reduction are achieved.