It is one of the important causes that the precision of the thread grinder decide the machining errors of the ball screw. The approach described in this study demonstrates how the dominant causes of the inaccuracies in thread grinding system can be determined. To evaluate the machining error of thread grinder, rotary encoder is allocated to spindle shaft and master screw for measuring the rotational transfer error between spindle shaft and master screw and the laser measuring system is used for checking the movement error.