As an important part of the cryogenic separation of ethylene plant, expander-recompressor is used to purify the exhaust gas in cryogenic zone and provide cooling capacity for the cold box in process system. It is the core equipment of the cryogenic separation system, and its long period and stable operation plays a vital role in reducing the ethylene loss of ethylene plant. This paper introduces the process flow and operational problems of expander-recompressor in ethylene plant, and puts forward some optimization and improvement measures based on the analysis of the operational problems, so as to ensure the stable operation of the expander-recompressor system.