Plastic shell accessory capable of preventing wire harness from loosening

The utility model belongs to the technical field of plastic shell accessories, and particularly relates to a plastic shell accessory for preventing a wire harness from loosening, which comprises a shell, the shell is through from front to back and comprises an upper shell and a lower shell which are mutually buckled along the vertical direction, and the top of the upper shell is provided with a threaded hole; the bunching mechanism comprises a first annular elastic piece, a second annular elastic piece, a telescopic assembly and an adjusting assembly. The lower end of the first annular elastic piece is open to accommodate the upper part of the second annular elastic piece, the upper end of the second annular elastic piece is open to allow a wire harness to be placed in, and the upper part of the second annular elastic piece can be placed in the first annular elastic piece and clings to the inner wall of the first annular elastic piece; the outer peripheral walls of the first annular elastic piece and the seco