Abstract: Aiming at the requirement of rapid inspection of crankshaft journal coaxiality, a method of visual measurement of coaxiality error based on 3D point cloud is proposed. In this paper, a laser scanner is applied to obtain the 3D point cloud model of the part to be measured, and the point cloud slices of equally spaced journals are calculated. After that, the Pratt-RLTS method is proposed to obtain the center of each point cloud slice, and then the common reference axis is obtained by the least squares method according to the center of each slice, which finally realizes the measurement of the coaxiality error. The experimental results show that the circle fitting method in this paper is more accurate and stable than the least squares circle method, the least-inclusive circle method, and the RANSAC method, etc. The average value of the maximum absolute error compared with the results of the coordinate measuring machine (CMM) is no more than 4.8 μm, which can satisfy the practical needs of fast and efficient measurement of the crankshaft coaxiality error.