The invention provides a positioning tool for machining, and belongs to the field of machining equipment. The positioning tool comprises a base plate, and compressing assemblies are arranged on the left side and the right side of the upper end face of the base plate in a staggered mode respectively; each compressing assembly comprises a compressing plate, a locking screw and a spring, wherein the compressing plate is horizontally arranged, the locking screw penetrates through the compressing plate to be connected with the base plate in a threaded mode, the spring and the locking screw are coaxially arranged, and the spring is arranged between the base plate and the compressing plate. According to the structure, a workpiece can be precisely positioned to be prevented from rotating, and the machining precision is improved.