Abstract: In order to improve static and dynamic performance of moving mirror motion system in Fourier transform infrared spectrometer, nonlinear PID controller based on disturbance observer was designed. Firstly, mathematical model of moving mirror driven system was established, nonlinear factors in the system were analyzed. And then the theoretical basis designing this controller was given. At last, numeral simulation and physical experiment were carried on. The experimental results show that, when moving mirror is moving at 133 mm/s, the maximum overshoot of system is 0, rising time was 3 ms, steady-state variance is 0.039 2 using NPID with DOB, which is obviously better than traditional PID controller. Conclusion shows that NPID with DOB controller is feasible and usable and it meets the requirement uniform motion of moving mirror.