Abstract: In view of problems of bad stability and low working efficiency of traditional control system of decanter centrifuge, a frequency-conversion speed-regulation and PLC control system of decanter centrifuge was designed. Design of frequency-conversion speed-regulation system of common DC bus, servo scheme and adjusting method of load rate of vice motor, PLC control system and configuration interface of the system were introduced in details. The actual application shows that the system runs stably and improves performance of centrifuge.