The invention discloses an arc extinguishing cover with protective parts for a dual-power supply automatic change-over switch. The arc extinguishing cover comprises a mounting frame, wherein the mounting frame is set into an N shape; the left side and the right side are vertical outer walls; the middle is connected with an inclined wall; arc extinguishing chambers are respectively arranged at two sides of the inclined wall; arc extinguishing plates are arranged in the arc extinguishing chambers; and the protective parts are arranged at arc inlets of the arc extinguishing plates. On one hand, the protective parts can effectively protect the arc inlets of the arc extinguishing chambers and the arc extinguishing plates at the arc inlets and reduce the damages to the arc inlets of the arc extinguishing chambers and the arc extinguishing plates at the arc inlets at high-temperature arc inlets; and on the other hand, the protective parts can generate hydrogen at arc-spraying high temperature; meanwhile, inner edges of the protective parts are set into an isosceles trapezoid with large arc inlets and large arc outlets; and the arc inlet speeds of the arc inlets of the arc extinguishing chambers are increased, so that arc extinguishing of the arc extinguishing cover is facilitated.