In order to improve treatment efficiency of coke plant wastewater with membrane bioreactor, this paper has discussed the treatment efficiency of coke plant wastewater with membrane bioreactor and contamination of membrane after added bioflocculant. Results show that after 6 days running, effluent water goes to stable, all of the concentration of phenols is below 10 mg/L, average concentration of phenols in effluent water is 3.95mg/L, and the lowest is 1.11mg/L. The removal efficiency of phenols keep to 98.9% at the end of run，and the highest is 99.6%. Concentration of NH3-N is maintained at 10mg/L，removal efficiency is 95.8%. Removal efficiency of COD comes to 96.5%, and the concentration of COD in effluent water is 43mg/L. At the beginning, the Flux of membrane is 14.3ml/min. At the end of running, it is 7.3ml/min with bioflocculant added, and it becomes 6.9ml/min with no bioflocculant added, which indicates that there is no evident effect of bioflocculant added on membrane flux.