The invention relates to an auxiliary device of a pneumatic impact wrench. The auxiliary device comprises a base plate, wheels, a cylindrical stand column, a rotating shaft, a bearing assembly, an upper limiting block, a lower limiting block, a suspension arm, a suspension ring and a load stretchable rod. The cylindrical stand column is vertically installed on the base plate, the rotating shaft is installed in the cylindrical stand column in a rotatable mode through the bearing assembly, an upper limiting opening is formed in the upper end of the cylindrical stand column, a lower limiting opening is formed in the lower end of the cylindrical stand column, the upper limiting block is connected with the upper end of the rotating shaft and extends out from the upper limiting opening, the lower limiting block is connected with the lower end of the rotating shaft and extends out from the lower limiting opening, the upper end of the suspension arm is hinged to the upper limiting block, the suspension ring is installed at the lower end of the suspension arm, the lower end of the load stretchable rod is hinged to the lower limiting block, and the upper end of the load stretchable rod is hinged to the middle of the suspension arm. The suspension ring at the lower end of the suspension arm can freely move in the horizontal direction and the vertical direction, when a nut is disassembled and assembled, labor is greatly saved, the auxiliary device is convenient to use, the labor intensity is greatly reduced, fatigue can be avoided, the locking degree is guaranteed, and the traffic safety is further guaranteed.