The utility model relates to an overhauling device of railway vehicles, in particular to an angle cock detecting clamping device, aiming to solve the problem that the overhauling device for detecting air tightness of the angle cock does not exist at present. The angle cock detecting clamping device comprises a front positioning sealing seat, a rear positioning sealing seat and a positioning bottom plate, wherein the rear surface of the positioning bottom plate is respectively fixed with a front bracket and a rear bracket; a clamping air cylinder is fixed between the front bracket and the rear bracket; and the front end of the clamping air cylinder is connected with an ejecting rod of the air cylinder. The utility model has the advantages of simple structure and reasonable design, solves the problem that the overhauling device for detecting air tightness of the angle cock does not exist at present, and is suitable for the air tightness detection of various angle cocks.