Tool capable of automatically turning nut

The invention relates to tool capable of automatically turning a nut. The tool is used to turn the fixing nut of the cable of a terminal box. The tool comprises a left cover body (2), a driving gear (10), a filtering gear I (13), two filtering gears II (16), an output gear (17) and a right cover body (1). The driving gear (10), the filtering gear I (13), the two filtering gears II (16) are installed on the left cover body (2). The driving gear (10) is matched with a ratchet (8). One end of the ratchet (8) is pinned on the left cover body (2) through a racket pin (9) and the middle of the ratchet (8) is fixed on the left cover body (2) through a set screw (6) and a compression spring (7). A wrench opening I (4) is arranged in the middle of one end of the left cover body (2). The output gear (17) is inlaid at the wrench opening I (4). A wrench opening II (18) corresponding to the wrench opening I (4) is arranged in the middle of the output gear (17). The right cover body (1) is arranged to be of a U-shaped structure. The right cover body (1) covers the left cover body (2). The invention has the advantages that the torsion of the tool capable of automatically turning the nut is fixed and the quality stability is good.