The Wheelset Online Monitoring Device is installed at vehicle depots, depot entry/exit lines, or on the main line. It employs light-section image measurement, high-precision displacement measurement, and other technologies, providing comprehensive monitoring and intelligent detection of the operating condition of vehicle wheelsets. It is used to issue early warnings for faults such as wheelset geometric dimensions, wheel flats (out-of-roundness), tread defects, etc., thereby providing technical assurance for the safe operation of urban rail vehicles.