The utility model discloses a positioning tool used for assembling an engine timing system and solves the problem that a positioning pin in the prior art is easily left in a positioning hole and is not easy to pull out after the torque of a camshaft chain wheel is tightened. The positioning tool comprises a timing pin and a handle, wherein two ends of the handle are provided with clamping arms, a free end of each clamping arm is provided with a bayonet, the timing pin comprises a pin body and a clamping head positioned above the pin body, the pin body and the clamping head are in a homogeneous integrated structure, a clamping slot in an annular structure is arranged between the pin body and the clamping head, and the bayonet and the clamping slot are matched. The positioning tool disclosed by the utility model has the beneficial effects that the time and the labor are saved in plugging and pulling the timing pin, the assembly efficiency of the timing system is improved, the timing pin is not easily left in the positioning hole, the positioning tool has a simple structure and is convenient to use and the like.