Abstract: In order to resolve the existing problems of adding flocculant such as poor effect of preparation,unreliable detection link,and poor real-time,the paper put forword a design scheme of auto-adding system of flocculant of medium-coal thickeners taking auto-adding system of medicament of medium-coal thickeners of Tianzhuang coal preparation plant as example.It introduced control principle,overall design,and software design of the system in details.The system can realize automatic control of adding volume of flocculant through detecting flow and turbidity of slime water.The practical application showed that the system realizes efficient and saving production and zero discharge of slime water,increases utilization rate of slime water,and eliminates pollution caused by slime water of preparation on environment.