Abstract: This paper focused on preparation of a new kind of dispersant used in coal water slurry（CWS）.It takes starch as raw material and is synthesized by grafted modification with acrylic acid and styrene to form a structure with a hydrophilic main chain and hydrophobic side chains.The optimum conditions of synthesis were determined by a series of orthogonal experiments.The effects of the dispersant on apparent viscosity and stability of Binchang coal of Shaanxi were discussed,and the mechanism of interaction between the dispersant and coal surfaces was analyzed.