With the unceasing speedup of the train in China, traffic safety has been closely related to people’s livelihood. As elements that determine the reliability and safety in railway traffic, wheel set must be detected with much accuracy. Based on scanning method, a portable measuring system for measuring profile of train wheels is presented in this paper. Scanning part, which is pulled manually, consists of an 1-D laser sensor, whose accuracy reaches 0.05mm, and a magnetic grid sensor, whose solution reaches 0.05mm. Every 0.05mm of magnetic head movement will make the 1- D laser sensor send its current data to the tablets to get the wheel profile. The geometrical parameters, including flange thickness, flange height, rim width and QR (which is representative of vertical wear) can be calculated once the scanning is done. The systematic errors and the random errors have been analyzed in this paper. After the error compensation, the repeatability error is below 0.05mm, and the measurement accuracy of each parameter is below 0.1mm.