This article studied the effect of different volume fractions of CO₂ (4% CO₂， 8% CO₂， 12% CO₂) on chlorophyll degradation of soybeans under 5% O₂ controlled atmosphere storage conditions. The results showed that controlled atmosphere storage could effectively delay the yellowing of soybeans and the decomposition of chloroplast ultrastructure， maintaining good appearance quality. During the storage process of soybeans， CO₂ treatment significantly inhibited the increase in the content of Chd a and Phb a in the deprotent medium， delaying the degradation of chlorophyll. On the 20th day of storage， the chlorophyll a/b content in the 8% CO₂ storage group was 40.32 μg/g and 20.37 μg/g， respectively， significantly higher than that in the control group. At the same time， the CO₂ storage group significantly inactivated the activities of MDCase and PPH， and at the end of storage， the enzyme activity of the 8% CO₂ storage group decreased by 19.8% and 7.2% compared to the control group， respectively. Therefore， the best effect of soybeans is achieved under 5% O₂+8% CO₂ controlled atmosphere storage conditions.