Objective: This study aimed to research the influence of different rotation speed of high-temperature compressor on the performance of NH₃/CO₂ cascade refrigeration system under various seasons and evaporation temperature of 25 ℃. Methods: The NH₃/CO₂ cascade refrigeration system model was established and its reliability was verified in this paper. The relationship between the rotation speed of high-temperature compressor and the evaporation temperature, the discharge temperature, the intermediate temperature, high-temperature compressor power, cooling capacity, Coefficient of Performance （COP） of cascade refrigeration system was calculated and analyzed. Results: The relative error of the simulation model for predicting the heat transfer was less than 14.1%. The cooling capacity of the system in spring, summer, autumn and winter respectively increases by 31.7%, 41.7%, 33.9% and 25.2% as the rotation speed of the high-temperature compressor increased from 2 300 r/min to 3 300 r/min, and the cooling capacity was the highest in winter in the low-speed range. In addition, high temperature compressor power showed a two-stage upward trend, increased by 40%～45%. Conclusion: There was a maximum COP and corresponding optimal high- temperature compressor speed. Based on the adaptability of the system to different seasons, a scheme of variable rotation speed NH₃/CO₂ cascade refrigeration system is proposed. Compared with the system with constant speed, the power consumption could be reduced by 19.9% per year.