This article focuses on the main operations during the shutdown of quench system of ethylene plant, and analyzes and studies the difficulties in emptying quench oil, the high oil content of quench water, and the easy blockage of discharge valve during the emptying operation. To solve the problem in emptying the quench oil, an optimization method is proposed for the emptying operation of quench system. By utilizing the height difference between the pipeline, tower tank and heat exchanger users of the quench oil system and the inlet pipeline of quench oil delivery pump and heavy fuel oil pump, temporary pipelines are configured to increase the number of available quench oil delivery pumps, improve the delivery flow rate, reduce the workload of operators, and effectively shorten the emptying time of the system and increase the recovery of quench oil. To solve the problem of high oil content of quench water, a method of preliminary separation and recovery of gasoline through cooling and settling is proposed. To solve the problem of easy blockage of discharge valve in the quench system, a backwashing method is proposed.