In order to study the influencing factors and rules of trajectory error,the machining path optimization and the trajectory error precompensation were carried out,and a trajectory error prediction method based on the identification model was proposed.The G code was interpolated by the lookahead interpolation module of the established numerical control system,and the discrete position instruction was obtained;the position instruction after interpolation was simulated machined by using the feed system identification model, and the output position was obtained;the machining trajectory error was calculated according to the interpolation position data and the simulation output position data.The simulation results show that by using this method,the value and distribution of the trajectory error during the joint processing of CNC machine tools can be quickly calculated,which provides methods and data support for the cause and rule analysis of the trajectory error,tool path optimization and the implementation of the trajectory error precompensation.