This paper studied the effects of controlled atmosphere(CA) with different CO₂ ratios (4% CO₂， 8% CO₂， 12% CO₂) on the appearance quality and chlorophyll degradation of Brassica chinensis L. under the condition of 4% O₂. The results showed that CA could effectively delay the yellowing of Brassica chinensis L.， reduce the weight loss rate and effectively maintain the appearance quality of Brassica chinensis L. Compared with the control group stored in the air environment， CA could significantly delay the degradation of chlorophyll a/b in Brassica chinensis L. On the 12th day of storage， the chlorophyll a/b content in the 4% CO₂ treatment group was 48.20 μg/g FW and 40.45 μg/g FW. 4 days before storage， the activity of chlase and MD was inhibited by CA， the activity of chlase in 4% CO₂ treatment group was 23.09 U/g FW， and MD was 43.03% lower than that in control group. At the later stage of storage， 4% CO₂ treatment effectively delayed the increase of the activity of PPH and Chl-POX， which were 5.49 U/g FWand 1.90 U/g FW. In general， the CA condition of 4% O₂ + 4% CO₂ seemed to be optimal for Brassica chinensis L. storage.