The invention relates to a gasoline and electricity hydrostatic composite hybrid power transmission system. The hybrid power transmission system comprises an engine, an absorber, a power distributor, a mechanical transmission module, a hydraulic transmission module and an electric transmission module. The electric transmission module comprises a generator, a motor and a power battery pack. Under a gasoline and electricity hydrostatic composite hybrid power transmission mode, the hybrid power transmission system can be converted into a mechanical-hydraulic shunt/co-current flow transmission mode, or a gasoline and electricity hybrid power transmission mode, or a motor-mechanical power transmission mode or a generator-mechanical power transmission mode. The hybrid power transmission system has an electricity-liquid hybrid power transmission mode, and can be further converted into a gasoline-liquid series connection transmission mode and a gasoline-electricity series connection transmission mode. The hybrid power transmission system has the steep hill retarding function of electric braking, hydraulic braking or electricity-liquid union braking, the auxiliary ramp starting function of electric braking, the function of starting or stopping the engine fast, and the function of charging the power battery pack in a plug-in mode.