With the rapid development of urban rail transit, the detection of track infrastructure is an important guarantee for ensuring the safe operation of trains. Gauge is one of the most important parameters in the track infrastructure. The change of the gauge distance will cause various vibrations of the train to change the wheel-rail force. It is the control factor that affects the safety and stability of the train operation, and is also an important reason for the damage and failure of the track structural components. With the increase of the operation speed of high-speed railways and the expansion of operation scale, it is an important task in rail transit safety work to master the information of gauge status and ensure the safety of rail transit transportation. However, most of the current gauge detection methods have problems such as high installation difficulty, large amount of data calculation, and expensive detection, and is difficult to achieve ideal effect in complicated dynamic environments. Therefore, this paper proposes a gauge detection method based on the relative movement of wheel and rail. This method uses the lateral variation of the left and right wheel pairs relative to the reference point to measure the gauge distance indirectly during the locomotive operation. Firstly, two laser cameras are used to respectively collect the laser spot image projected by the laser source into the left and right gauge detection area, and then the perspective correction transformation matrix is obtained through coordinate transformation according to the positional relationship of the corresponding feature points in the reference time image and the detection time image and through the transformation matrix. The detection time image is corrected to obtain a front view image which is unified with the acquisition time at the reference time. The horizontal swing during the locomotive operation is much larger than the vertical vibration. Therefore, we accurately extract and locate the center point position of the laser spot. The mathematical transformation is established by the vertical displacement change of the laser spot center point in the two-track gauge detection area. The change of the relative movement between the wheel and rail on both sides of the reference time is obtained by calculation, and the gauge detection is finally realized. We verified and evaluated the gauge detection method proposed in this paper through multiple sets of dynamic experiments and using a variety of evaluation indicators. The experimental results show that the maximum error of the gauge detection method is less than 1 mm, which can meet the requirements of high-speed track detection as stipulated by China Railway Corporation. The detection device composed of simple structures is easy to install. In addition, the device has high robustness to a complex environment, and has certain practicability.