The utility model designs a dustproof anti-rotation belt tensioning wheel to solve the technical problems that a tensioning wheel is short in service life, a gasket is inconvenient to use and the like. The damper comprises a body, a supporting plate and a damping piece connecting the body and the supporting plate. The damping piece comprises an anti-attrition plate and an extension edge connectedto the outer ring of the anti-attrition plate. the thickness of the extending edge is greater than that of the anti-attrition plate; according to the utility model, the damping piece adopting a bidirectional flanging structure is added between the support plate and the main body; dust and foreign matter can be effectively prevented from entering the damping piece, meanwhile, the contact area of the damping piece is increased, the pressure borne by the damping piece is effectively reduced, the service life of the damping piece is prolonged, the limiting convex points of the damping piece are connected with the limiting pits in the body in an assembled mode, and the damping piece can be effectively prevented from rotating due to limiting of the limiting blocks and the limiting grooves.