Abstract: For advancing the motion accuracy of the PRS-XY type hybrid CNC machine tool developed in Beijing Institute of Technology,using a ballbar,the motion ability of its X-Y table was tested.Because of limited working area,the bar had to be inclined.The circular track of motion was tested,and the most important factors affecting the motion accuracy,vid.,errors in perpendicularity and proportion matching,were confirmed.Models of error calibration have been set.Using new characters of the Turbo PMAC card,error calibration has been realized.Abilities of motion has been improved,and the accuracy of motion has been advanced over ten times.