Abstract: In coal slurry water treatment, addition of reagent is generally necessitated for improving slurry sedimentation effect and ensuring the realization of a class-A closed washwater circuit. However, the automatic reagent dosing systems traditionally used cannot work so satisfactorily as expected. Based on result of analysis of the characteristics of such dosing systems, and through internal model control system modeling and making online identification of parameters using particle swarm optimization(PSO) algorithm, an IMC-based automatic reagent dosing control system is developed. Result of study shows that the system can work with a higher response rate and much improved control effect as compared with the traditional PID control system, and its use can lead to elimination of time-lag problem.