Cracking gas compressor is a critical unit in ethylene plants. The unplanned shutdown of cracking gas compressor due to operational failure will cause incalculable losses to the production of ethylene plants. Therefore, the good operation of cracking gas compressor is crucial for the smooth production of ethylene plants. With the extension of operating time of the cracking gas compressor unit of a company, problems emerged in various components of the compressor unit. The problems of cracking gas compressors found during the overhaul, including the serious wear of water injection nozzles, the coking in cylinder body and flow passages, and the corrosion of shaft seal gas seal, were tackled and eliminated one by one, ensuring that the “5-year overhaul” target of cracking gas compressors can be met.