Abstract: The problem of membrane fouling of ultrafiltration caused by the municipal middle water running in the boiler feed water system of one thermal power plant of Shenhua Guoneng Energy Group Co., Ltd. was studied. The running data of ultrafiltration, the municipal middle water quality index and the fouling matter from ultrafiltration were comprehensively analyzed. It is found that the main reason for the membrane fouling of ultrafiltration is the over-standard of COD_Cr and NH₃-N in the middle water from the wastewater treatment plant. The adjustment of the running conditions can be an effective measure to reduce the membrane fouling of ultrafiltration. Through the adjustment of the condition parameters, the trans-membrane pressure and the water inflow of ultrafiltration membrane can meet the operation requirements of the thermal power plant, indicating that this measure can effectively reduce the membrane fouling of ultrafiltration.