To improve the detection precision of the urban rail vehicle wheel key parameters, a new non-contact dynamic detection method based on opening up a “detect window” at the wheel/rail contact point is put forward. The image geometric mapping model of the wheel tread and the coordinate system for detection are established, and the calculation method of wheel key parameters is established on the basis of coordinate translation methods. According to the actual application regulations of urban rail vehicle wheels, the key parameters of optical section detecting window are selected. The wheel key parameters checking experiments are carried out by use of the developed test bed. The results show that the wheel key parameter error values obtained by the method are all less than 1％. By opening up the “detect window” at the wheel/rail contact point, the light source position and the camera position can remain unchanged, so the parameters detecting precision can be guaranteed effectively.