The utility model relates to a big moment of torsion dismouting device to threaded connection spare, including base, hydraulic motor, the speed reducer is connected to hydraulic motor's output, and the speed reducer is installed on reducer bracket, and reducer bracket's the height -adjustable festival bolt assembly that passes through installs on the connecting plate, and the upper surface of baseis equipped with left and right limit baffle board, and the axle head fixed mounting of the transmission shaft of speed reducer has the toggle, is equipped with the spout, the adjustable round pin axle of installing in the spout along radial direction on the toggle, be equipped with the curb plate before the upper surface of base after, in the front, be equipped with left connecting plate and right connecting plate between the posterior lateral plate, wear to be equipped with horizontal adjusting bolt on right connecting plate, be equipped with connecting seat, horizontal adjusting bolt swingjoint connecting seat on being close to right connecting plate. Adopt above -mentioned technical scheme, have structure integrate, the reliable operation, work efficiency is high, and output torque is high to can use in the dismouting of the especially big threaded connection spare of the big moment of torsion of needs applicable very much at the torque value of steplessly adjust output shaft rotation rate and infinitely variable control output.