Abstract: Aiming at the problems of low detection efficiency and insufficient detection accuracy of wheel outer diameter measurement on the finished wheel inspection line of Masteel train, a non-contact wheel outer diameter measurement system and method based on laser ranging is proposed. The position of the four lasers is calibrated by calibration pointer and calibration ring, and the wheel tread diameter is obtained by measuring data and geometric relationship of the four lasers. The measuring system can measure wheels from ϕ800 mm to ϕ1 300 mm, with a measurement accuracy of less than 0.5 mm, and this method can also be applied to the measurement of the outer diameter of disc parts.