In order to improve the quality of dried Agaricus biporus slices, a small modified atmosphcric dryer developed by the authors was used to conduct the experiment for the slices of Agaricus biporus, in which CO2, N2 were used as drying media to replace partial air. The effect of Controlled Atmosphere Drying (CAD) and hot air drying on the drying speed and product quality of the dried products was analyzed. The results showed that the slices of Agaricus biporus with CAD in drying process filling N2 to replace partial air not only the highest drying rate could be obtained, but also could get the mass fraction of vitamin C was better, the mass fraction of ADF was losing, and could obviously reduce browning degree, the fiavour and quality of the Agaricus biporus were satisfactory.