The invention relates to a liquid-viscosity loading system which is suitable for applying load moment to the rotating shafts rotating at various speed. The liquid-viscosity loading system mainly comprises a hydraulic control system and a liquid-viscosity loading device which is connected with the hydraulic control system. The hydraulic control system comprises an electric motor, an double pump, an electrohydraulic proportional overflow valve, an electromagnetic reversing valve, a filter, a pressure detecting element, a pressure gauge, a lubricating oil tank and the like. The liquid-viscosity loading device comprises an inputting shaft, a piston, an external friction plate, an internal friction plate, a resetting spring, a shell, an end over, a sealing cover, a sealing assembly and the like. The power is transmitted by using the viscosity of the lubricating oil film between the friction plates or the shearing force, the load moment is regulated by changing the thickness of the lubricating oil film, a lubricating oil passageway is formed in such a way that the electric motor drives the double pump to be connected with the liquid-viscosity loading device, and the lubricating oil pressure and the load moment are controlled through the electromagnetic reversing valve, the electrohydraulic proportional overflow valve and the like. The liquid-viscosity loading system has the advantages of simple structure, steady loading, long service life, convenient operation and good effect.