The harmonic characteristics of linear motor drive circuits for mechanical crycoolers are studied. Selecting a 150 W linear motor as the research object, the harmonic analysis of its output voltage is carried out by theoretical simulation and experimental verification. The influence of the filter design on the harmonic characteristics of the drive circuit is explored. The filter is optimized by studying the relationship between the changes of inductance L and capacitance C of the filter and the output harmonics. The optimized filter is improved greatly in performance. The Total Harmonic Distortion (THD) of the output drive is reduced from 4% to 1.96%.