Abstract: With an aim to simplifying the process for the tuning up of the parameters of the PID controller of the dense medium density control system for better control performance of the control system,an investigation is made into the feasibility for PID system to effect self- searching optimal control using the simplex method,so as to cater to needs for the control of the density of heavy medium suspension. As evidenced by analysis of the performance of the control system,the use of the digital controller so designed can realize not only signal conversion but also calculation of performance indexes and automatic optimization of parameters of PID controller.