Wheel set is an important part of the train, whether the key parameters of wheel set tread exceed the limit is related to vehicle driving safety. Therefore, it is necessary to regularly detect the wear condition of the train wheel set. A method for measuring wheel set tread profile is proposed, in which the design of measurement system and improved gray center algorithm are included. On this basis, a simulation wheel set tread detection experimental system is established to test the result. It is shown by the experiments that the mean square error (MSE) of the 1~10 mm block gauge is within ±0.1 mm, and MSE of the 1~5 mm is less than 0.05 mm, which can meet the high precision requirements of industrial measurement.