Abstract: Phanerochaete chrysosporium were used to investigate flocculating effects of coal slurry with orthogonal experiments.The study results indicate that Phanerochaete chrysosporium have a good effect in flocculating coal slurry,the optimum combination of Phanerochaete chrysosporium culture time is 2 days,coagulant is 2 mL,and bacilli volume is 2 mL,the kind flocculent is broken liquid,the pH value is 6.The result of FTIR shows that the biological extract of Phanerochaete chrysosporium contains a lot of acidic polysaccharides that has the effect of flocculation.Microbial flocculent molecule and coal slurry particle could flocculate by "absorption bridge",finally deposited.