In order to improve the measurement quality of ABS gear detector, according to the measuring principle, the structure feature and the reason of error produced during measuring, the basic factor influencing the measurement accuracy is analyzed in this paper. And an error correction method based on the principle of least square curve fitting and affine transformation of space rectangular coordinate is developed to solve the key problem of error production, which could improve measuring accuracy without affecting mearing speed. At the same time a mathematical model is built according to the measuring principle. The result of simulation by MATLAB7.10 proves that the error correction method is correct and feasible. The calculation proves that the measurement repeatability and uncertainty of ABS gear detector after error correcting is acceptable. It proves that the error correction method can be used into the ABS gear detecting system, and has high practical value.