Abstract: In order to understand track irregularity of high-speed railways,and to guaranteeitsoperation safety,dy-namic simulations of one type of high-speed electric multiple unit(EM U)are carried out.Specifically,the influences of track irregularity wavelength and amplitude on vehicle dynamic performance are analyzed to determine the ranges of irreg-ularity wavelength,which requires special attention during track maintenance.For simplification,the track irregularity is converted to vertical profile,track alignment,track cross-level,and track twist irregularities of harmonic wave with dif-ferent wavelengths and amplitudes,and simulations are carried out based on a vehicle-track coupled dynamic model.The results show that the irregularities withinshort and mid wavelength range havesignificant impacton wheel/rail dynamic in-teraction and the safety and smoothness of train operation,which is mainly caused by the irregularities within mid and long wavelength range.The vehicle dynamic force has a linear positive relationship with the irregularity amplitude,and the change of irregularity amplitude undersensitive wavelength has significant influences on system dynamic.Analysis re-sults determine the sensitive wavelength ranges of track irregularity and corresponding influence of its amplitudeof the specific type of high-speed EMU,which highlights the key points of track maintenance,andhelpful for improvingmainte-nance efficiency as well as operation quality of EMU.