An ethylene plant expanded its production capacity from 800 kt/a to 1 100 kt/a in 2020. Since the beginning of this operation cycle, the steam turbine of cracking gas compressor, the core equipment in ethylene plant, has successively encountered some problems such as low inlet pressure, low flowrate ratio of extracted steam to condensed steam and increased vibration of the unit during high-load operation, affecting the safe and stable operation of the unit and the whole plant while increasing the energy consumption of the unit. This paper analyzes the reasons for these problems and makes quantitative calculation, identifies the specific reasons, and puts forward relevant suggestions for further transformation and optimization.