The wheelset size and tread detection system realizes dynamic and accurate measurement of the geometric dimensions of the wheelset tread wear, rim thickness, rim height, wheel diameter, inside distance of the wheelset, OR value, out-of-roundness, etc. of metro trains through non-contact 3D point cloud reconstruction measurement technology, and accurately identifies the fault of wheelset tread scuffing through infrared image stitching technology. The system has strong resistance to environmental interference and harsh working conditions, and is suitable for the automatic detection of all types of subway train wheelsets.