Fourier transform infrared(FTIR) spectrometer takes significant role in monitoring the earth's environment and atmospheric pollution. Michelson interferometer is the main part of FTIR spectrometer. In order to provide uniform motion of the interferometer mirror, stability and repetitiveness of sampling, a servo system based on ATMEL89c52 single-chip is described. With the help of laser interference and white light interference, it achieves not only uniform velocity but also precise position through PID controlling, which satisfies the spectrometer's motion demand.