Because cracking gas has complex components and contains olefins, high molecular olefins and sulfides, the heavy components, especially butadiene, will rapidly accelerate the polymerization reaction at high temperature, and the polymerization reaction is very easy to occur, seriously affecting the mechanical performance and efficiency of cracking gas compressor and shortening the operation cycle. In order to reduce the high temperature scaling of compressor impeller, water injection is needed to reduce the temperature. Metering pump, which was designed for water injection, has many defects. After optimization, boiler feed water pump is used to supply water, overcoming the defects of metering pump. Ensuring the continuous and stable operation of water injection system is critical for reducing the outlet temperature of compressor, slowing down the coking rate and prolonging the operation cycle of compressor unit.