In order to improve the measuring precision and efficiency of noncircular gear, a new idea of measuring with coordinate measuring machine was put forward.According to the characteristics of noncircular gears which were different from circular gears, the error projects for noncircular gears were put forward.By calculating the tolerances of cylindrical gears, a method for calculating the tolerances of the noncircular gears was found.The suitable probe was selected and the measuring path was planned.The measurement of toothtooth scanning of noncircular gear was realized by using the three coordinate measuring machine so as to obtain the profile data value of noncircular gear.On this basis, the data value was fitted and calculated by curve, thus the error of noncircular gear was obtained.