The workpiece quality that the CNC machine table hold at runtime is often different and changes in range. The workpiece quality change has great impact on the performance of the linear motor servo system. The CNC machine table linear motor servo system overshoot and adjustment time in case it drove workpieces with different quality were analyzed. The relationship between the system overshoot and the workpiece quality was found out. Nonlinear PID control was used to suppress overshoot in the case of a certain quality of the workpiece. And the adjustment time was cut down. the The corresponding relationship between the nonlinear PID control parameter Kd and workpiece quality was found out. With linear fit, nonlinear PID control parameters could be adjusted. So better response performance can be achieved in different workpiece quality.