The ethylene plant at PetroChina Fushun Petrochemical Company resumed operation after 5 years of shutdown. The heat transfer effect of heat exchanger gradually decreased and the water quality of circulating water became worse, affecting the stable operation of the plant at high load. Based on analysis and research, some corresponding measures were taken to improve the water quality of circulating water. During the overhaul in 2021, the impurities in heat exchanger and circulating water pipeline were thoroughly removed, and the circulating water system was revamped to solve the bottleneck problem, thus achieving the stable and up-to-standard quality of circulating water and promoting the long-term operation of the plant at high load.