Abstract: This paper expounds a real time expert control system for cement rotary kiln The control system for cement rotary kiln consists of two parts:base automation and process automation.It suits to the situations of long delay,serious non linearity and difficulty to measure of parameters in the process of cement rotary kiln and simplifies the rules.In combination with the reality of the control system for cement rotary kiln,this paper describes the representation of knowledge and the algorlthm of inference machine.