The invention discloses a grinding tool for a weld seam of a feed port of a dustproof cover of a rotary vibrating screen. A motor and a speed reducer are arranged on a worktable board and are fixedly connected. A driving belt wheel is arranged on an output shaft of the speed reducer. One side of the motor is provided with two sets of rotating shaft supports arranged in parallel. A rotating shaft is fixed in the rotating shaft supports. One end of the rotating shaft is provided with a driven belt wheel opposite to the driving belt wheel. The driving belt wheel and the driven belt wheel are connected through a belt. A dustproof cover fixing plate is fixed to the other end of the rotating shaft through a connecting flange. A plurality of sets of spring bases are uniformly distributed on the position, close to the edge of the dustproof cover fixing plate, of the outer side of the dustproof cover fixing plate in the circumference direction. A spring is arranged on each spring base. A hook used for hooking the edge of the dustproof cover is arranged at the tail end of each spring. A positioning block matched with the feed port of the dustproof cover is arranged in the middle of the outer side of the dustproof cover fixing plate. According to the grinding tool for the weld seam of the feed port of the dustproof cover of the rotary vibrating screen, the labor intensity of workers is effectively reduced, the grinding efficiency of the workers is improved, and the smoothness consistency of the welding seam of the feeding port of the dust cover of the rotary vibrating screen is ensured.