Method and system for detecting train wheel diameters

The invention discloses a method and a system for detecting train wheel diameters. The method comprises the following steps: receiving a group of time sequences generated when train wheels pass by through laser emitting-receiving devices; calculating an instantaneous velocity at which the wheels pass by firstly in conjunction with field mounting parameters; calculating chord lengths of lasers on the wheels through the velocity; lastly, calculating the wheel diameters through a corresponding algorithm. According to the method and the system, only two laser emitting-receiving devices need to be adopted, so that a large amount of cost is saved; the instantaneous velocity of a train can be obtained without any additional train velocity detection device; the two laser emitting-receiving devices can be used for calculating the wheel diameters separately, and results are averaged, so that errors can be reduced greatly.