Abstract: Due to the effluent from wastewater treatment system of Yumen Refinery could not meet the emission standard steadily, some countermeasures were adopted, such as revamping the regulating pool, building north sewage lifting pool, enhancing the removal rate of floating oil, applying pressurized dissolved air floatation, using new anaerobic biological treatment, combining peristaltic bed and BAF treating technology and setting up a new sludge treatment system. Since then, the quality of total discharge water is improved greatly with hydrocarbons of 0.71 mg/L, COD of 54.0 mg/L, BOD5 of 29.7 mg/L, sulfide of 0.02 mg/L, suspended solids of 14.67 mg/L, cyanide of 0.04 mg/L, ammonia-nitrogen of 0.48 mg/L, volatile phenol of 0.27 mg/L and pH value of 7.37, which well meet the requirements of national emission standard (GB8978-1996) and it also provides the feasibility of recycling discharge water.