The invention discloses a high-power hydraulic variable speed transmission device, which comprises an integral torque converter and a planetary speed changer, wherein an input flywheel, a locking clutch and a power taking device are also arranged in the torque converter; four planetary row assemblies, four brakes and two rotating clutches are arranged in the planetary speed changer; all parts are connected through splines or gears; the two rotating clutches and the four brakes are used for realizing different control; the gear requirements of eight forward gears and a neutral gear can be realized; the gear number can be reduced by decreasing the number of planetary rows and the brakes. The high-power hydraulic variable speed transmission device has the advantages that the application power is great; the structure is compact; the deformation is easy; the whole machine arrangement is favorably realized.