The invention provides a sliding mechanism applied to a portable electronic device. The sliding mechanism comprises a body, an outer frame piece, a protective window and a cover body, wherein the outer frame body is arranged on the body; the protective window is fixed between the outer frame body and the body; the cover body is accommodated in the outer frame piece in a sliding way and comprises two opposite sliding rails; each sliding rail has a surface in sliding contact with the protective window; a part, which is contacted with the protective window, on the surface is provided with a plurality of linear stripes; and the extension direction of the linear stripes is parallel to the sliding direction of the sliding rail. The sliding mechanism has high sliding performance and a simple structure.