Abstract: In order to explore the degradation law of wheel diameter value of urban rail vehicle wheelsets and effectively evaluate the reliability of wheelsets, this paper proposed a wheelsets reliability evaluation method of urban rail transit vehicles based on Wiener process. The paper selected the wheel diameter value as the performance degradation index, and established the wheelset degradation model of urban rail vehicles based on the Wiener process. By calculating the remaining life of the wheelset, the paper selected the degradation model with the highest accuracy to evaluate the reliability. Aiming at the complex problem of calculating the posterior distribution formula of the parameters of the degradation model, the paper used the Markov chain Monte Carlo (MCMC) method to solve the problem. Based on the actual measurement data of the wheel sets of trains on Guangzhou Metro Line 8, the verification results show that urban rail vehicles should ensure that the reliability of the wheel sets is not less than 0 9. After turning and running to 275 100 km, the degradation of the wheel set should be checked to ensure the safe operation of the vehicle.