Abstract: Based on the problems of poor water quality of black water from coal water slurry gasification, system pipelines and heat exchanger scaling and others t 0 control gasification device long-term stable operation in Datang Hulunbuir Chemical Fertilizer Co., Ltd., the author introduced the operation of lignite gasification devic e, described the black water treatment process and the flocculation mechanism, and studied the selection and optimization process of organic polymer flocculant.The re sults showed that there was a good better effect for cation polyacrylamide to treat black waster water. When the mass density of cation polyacrylamid added for 0.8 mg/ L, the balck water turbidity index was less than 30 NTU, suspended matter index was less than 30 mg/L, which met the requirements of operation conditions, and could ensure the long period operation of gasification device.