Abstract: Coal slime water could be called the “blood” of coal preparation plant,and the circulating coal slime water system is the “blood circulation system” of coal preparation plant.In order to systematically introduce the properties of the circulating coal slime water system of the coal preparation plant,the concept of water chemistry in coal preparation is proposed.The water chemistry properties of circulating coal slime water system are com prehensive understood by introducing the material composition of circulating coal slime water system,the disso lution of inorganic salt minerals,the oxidation of inorganic sulfur in raw coal,the hydrolysis and polymerization of metal ions,the acid base reaction of coal slime water,and the adsorption of metal ions by clay minerals.The mineral composition of raw coal is a key factor affecting the water chemistry properties.The water chemistry properties are changed after a series of chemical reactions in the circulating slime water system,including ions composition and content,acid base system of coal slime water,and occurrence mode of ions.The adsorption of metal ions by clay minerals has an important impact on water chemistry properties,which ultimately makes the content of high valent metal ions reduced in coal slime water.The adsorption form of metal cations on clay minerals includes electrostatic adsorption,hydroxyl complex adsorption and precipitation adsorption.The adsorption forms of metal ions on clay minerals are analyzed theoretically.At the same time,the adsorption process is also affected by pH,which ultimately reduces the content of high valent metal ions in the coal slime water.Through the reaction principle,influencing factors and experimental simulation,each reaction process is analyzed separately,and the correlation between the various reactions is summarized.It is concluded that the above multiple factors influence and restrict each other,which collectively determine the water chemistry properties of the circulating coal slime water system.The understanding of the water chemistry properties of the circulating slime water system is the basis for efficient coal preparation.The changing law of water chemistry under different coal samples and water quality environmental conditions can be obtained.The precise control of water chemistry properties can effectively improve the coal slime flotation and coal slime water settlement.