Aiming at the problem of The leakage of propylene heat exchanger leakage in the long-term production and operation of coal-to-olefin project,when the propylene heat exchanger in the circulating water system leaks, the phenomena such as the increase of oxidizing bactericide dosage, the change of cooling tower and tower pool, the change of COD in the system, the alarm of toxic and combustible alarm and the change of circulating water heat exchanger were summarized, the influencing factors such as circulating water system operation, system design and daily operation of circulating water were analyzed, and the preventive and improvement measures were put forward to ensure the long-term stable operation of the system.