Abstract: To improve the quality of dried Agaricus bisporus segments, CO₂ or N₂ were applied by replacing parts of air as drying media in the dehydration experiment. Self-made controlled atmosphere drying equipment was used in this experiment. The effects of different drying media on the quality of the dried mushroom were evaluated by using an orthogonal experiment. The results show that when the air is replaced by N₂, the dehydration ratio of Agaricus bisporus segments is improved, while Vitamin C degradation and discoloration reduced. Regression analysis shows a confidence level up to 95% on the correlation among the degree of browning, Vitamin C retention rate, ADF change, O₂ content, drying temperature and time. The results are valuable for practical applications.