Profile of the path of contact ( PPC), as a characteristic curve on the gear tooth surface, is with specific engineering significance. It can reflect the quality of gear machining and gear transmission. The PPC is not only the generative curve in gear hobbing, worm grinding and other generative machining, but also the working curve in the involute gear transmission. However, there is no function to measure the deviation of PPC for the existing gear measuring instruments. The theoretical model of the PPC is presented, which is based on the gear geometry. By means of the existing gear measuring center, the four-coordinate method and the threecoordinate method for measuring the deviation of PPC are proposed. The measurement practice indicates that the measurement and evaluation of the PPC can be realized by using the existing gear measuring instruments. The form deviation, slope deviation and total deviation of the PPC measured by the four-coordinate method are 0. 2, 1. 3, and 0. 6 μm, which are different from those measured by the three-coordinate method. Compared with the gear involute and helix, the PPC has features of comprehensiveness, unity, and uniqueness. The optimal deviation of PPC is obtained through synthesizing the involute deviation and helix deviation of the gear, which effectively reduces accuracy requirements for the gear involute and helix.