Abstract: This paper studies the CAT (computer-aided testing)technique with supper computer used in on-line high-precision measurement and data processing system for spindle rotation accuracy.The system consists of maset-ball,general-purpose instruments,supper computer and a set of software's for data processing.Based on eccentricity elimination by digital filter,data processing and error evaluation are discussed.The system is applied in the study of the spindle rotation accuracy of a matching tools' axs.The results of the rotation error are given.