The cracking gas compressor of the 220 kt/a ethylene plant of PetroChina Dushanzi Petrochemical Company was put into operation in 2021 after overhaul. After 11 months of continuous operation, some problems emerged such as the high first-stage suction pressure, the increased M factor of compressor and the fouling of interstage cooler. By optimizing the wash oil medium of compressor and changing the polymerization retarder, the M factor growth was effectively prevented, and the coking trend of compressor impeller and flow path was delayed. In view of the rising pressure difference of interstage cooler of cracking gas compressor, the influence of interstage resistance drop on compressor power was effectively reduced by installing isolation valve, monitoring pressure difference trend in real time and switching off a single furnace for decoking.