Abstract: Taking humic acid as a raw material, acrylic acid as graft polymerization monomer and potassium persulfate as an initiator, the solution polymerization w as applied to prepare humic acid-acrylic acid graft copolymer and to detect and measure the viscosity of the coal water mixture, fluidity and stability affected by the graf t copolymer.With the orthogonal experiment, the synthesis optimized conditions of the humic acid-acrylic acid graft copolymer were obtained.The mass ratio of acrylic a cid and humic acid was 0.35 : 1.00, the initiator dosage was 5%, the reaction temperature was 75 °C, the reaction keeping time as 2 h and the humic acid-acrylic acid graft copolymer would have excellent dispersing performances to the coal water mixture with Binchang coal in shaanxi.When the dosage of the dispersant was 0.12%, t he apparent viscosity of the coal water mixture was 956 mPa.s.