The invention relates to a positioning steel ball anti-drop device which comprises a guide rod, a sleeve and a steel ball, wherein the sleeve and the guide rod are of an assembled structure; the sleeve is of a hollow tubular structure; a lug boss used for limiting the steel ball is arranged at one end of the sleeve; the steel ball is arranged in the sleeve; and one end of the guide rod penetrates into the sleeve, and is fixed by a positioning pin. The positioning steel ball anti-drop device provided by the invention has the advantages that the sleeve and the guide rod are subjected to cold machining, the machining precision and the assembling precision are easy to control, and the technological process is relatively simple; an assembled steel positioning mechanism is adopted, and can be conveniently dismounted and replaced when the structure is damaged, so that the maintainability is high; and meanwhile, the assembled steel positioning mechanism is stable in performance and reliable to work, and the problem about dropping of the steel ball is thoroughly solved.