Based upon GDAS and GBL NCEP reanalysis data with resolution 1°×1°and 2.5°×2.5°respectively,the trajectory of the air mass at 100 m altitude over Hetian meteorological station is simulated by HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model),which is developed by Air Source Laboratory of NOAA,to estimate the effect of integration error and resolution error on the trajectory calculation error.The contribution of the integration error is found to be very small,which increases slightly with the integration time length and has no relation to the resolution of the meteorological data.The resolution error varies at different time point,and is found to be related to the topography,the weather system and the interpolation.The simulated trajectories using datasets with different resolution differed with each other significantly,indicating that the resolution error contributes more to the trajectory calculation error than calculation error.