The invention discloses a workpiece inner hole positioning tool. The workpiece inner hole positioning tool comprises a pedestal, a plurality of slide bases and a core shaft, wherein the center of the pedestal is provided with a cylinder; a first through hole which penetrates through the top surface of the cylinder and the bottom surface of the pedestal is formed in the cylinder; the core shaft is movably assembled in the first through hole; the core shaft is provided with a reducing section; second through holes which are as many as the slide bases and communicate with the first through hole are horizontally formed in the circumferential direction of the side wall of the cylinder; a steel ball is arranged in each second through hole; the diameters of the steel balls are greater than the wall thickness of the cylinder; the slide bases can be movably arranged on the pedestal and are aligned with the corresponding second through holes in a radial direction; and when the core shaft moves up and down, the slide bases can be pushed to move in the radial direction of the pedestal through interaction of the reducing section and the steel balls. The workpiece inner hole positioning tool has the beneficial effects that: the hole wall of the inner hole of the workpiece is quickly jacked by the slide bases through the matching of the core shaft and the steel balls, the steps in the positioning process are extremely simple, the structure is delicate, the positioning is reliable, and the automatic popularization and application can be realized on a large scale.