A denoising optimization method for an AC traction motor by chamfering a stator tooth shoulder includes taking an angular vertex of the stator tooth shoulder as an end point, obtaining two points equidistantly along two sides of a stator tooth shoulder angle from the end point; and using the two points as tangent points D1 and D2 of the inscribed arc; making the inscribed arc of the tooth shoulder angle through the two tangent points D1 and D2, cutting off the tooth shoulder angle along the inscribed arc, and adjusting an oblique height HS1 of a stator tooth pole shoe. The invention obtains optimal values of a chamfering size and oblique height of a stator tooth slot pole shoe by adjusting the oblique height of the stator tooth pole shoe and adopting a particle swarm optimization algorithm.