The weld irregularity of the rail on a highspeed railway in China before and after grinding was measured by using the Railprof,and the change of the weld area geometric irregularity was analyzed.It is shown that the rail grinding can reduce the amplitude of weld irregularity. Based on the vehicletrack coupled dynamics theory, the highspeed vehicletrack coupled dynamics model was established,the characteristic of the wheelrail dynamic response due to the rail weld irregularity was investigated, and the effect of the train speed on the wheelrail dynamic response was also discussed. Results show that wheel/rail vertical force is increased with the increasing of train speed.The wheel/rail vertical force and reduction rate of wheel load are significantly reduced after rail grinding.The amplitude of weld is decreased and the weld irregularity is improved after rail grinding, so the dynamic performance and security are improved.