The invention provides a top-cap structure and a railway wagon with the top-cap structure. The top-cap structure comprises a vehicle frame, a travelling assembly and a dust cover, wherein the vehicleframe is provided with guide rails arranged oppositely; the travelling assembly is arranged on the vehicle frame, and can slide along the guide rails; the travelling assembly comprises a top-cap crossbeam and a guide frame connected with the two ends of the top-cap cross beam; the guide frame comprises a frame, an idler wheelrollablyarranged in the frame and a positioning block arranged relativeto the axial direction of the idler wheel, the positioning block is arranged on the frame, a semi-closed structure is enclosed by the positioning block and the idler wheel, and is used for installingthe guide rails, and the idler wheel can slide along the guide rails. The displacement of the guide frame is limited through matching of the positioning block and the guide rails, it is guaranteed that the guide frame cannot be separated from the guide rails in the harsh environment such ad gale or in the case of irregularity of the guide rails, thus the guide frame can slide along the guide railsreliably, then the safe operation of the top-cap structure is ensured, and the usability of the top-cap structure is improved.