In view of the complexity of the conventional control of scanning mirror based on a digital-analog hybrid design, this paper focuses on a concise and efficient control method around the completely digital signal. The quadrate-encoder pulses A and B generated by the scanning mirror were sent into CPLD pins where an algorithm on position control and velocity control had been built. As a result, the CPLD will generate two PWM signals. These two signals are regenerated by a digital power chip to drive the voice of motor bundled with the moving mirror. Experiments validated that the stability of velocity of moving mirror is better than 97.2% and the method can improve the SNR of the measured spectrum and guarantee the accuracy of spectral qualitative and quantitative analyses.