It's hard to employ traditional time-frequency analysis methods to improve both time and frequency resolution when analyzing the non-stationary random vibration of suspension systems. Therefore， obtaining the vibrational characteristics， especially in time and frequency domain simultaneously has always been a key problem. This paper proposes a new non-uniform modulation function combined with the non-stationary pseudo excitation method to solve the previous problem. A general model of non-stationary pseudo excitation for a single wheel is established through the new non-uniform modulation function. Then， the difficulty in the time difference between the front and rear wheels is solved based on the covariance equivalence of stationary and non-stationary processes. Also， a half vehicle model is established， and the evolutionary power spectrum of the vertical acceleration is computed which shows a higher resolution distribution in time-frequency domains. Finally， two cases of vehicles traveling at constant and varying speeds are studied and the results show that when the vehicle travels at a varying speed， the increased speed will result in the expansion of the resonance range. Hence， this conclusion is of great value for improving vehicle ride comfort.