Abstract: Taking the bacterial bag of Hypsizygus marmoreus in the ripening stage（60-120 days） at test material, three treatments with different CO₂ concentrations, low（0.05%-0.20%）、medium（0.35%-0.50%） and high（0.70%-1.00%） level of CO₂ concentrations were set, the effects of the CO₂ concentration to the upper、middle and lower parts of the package yield were studied, the optimum concentration range of CO₂ was drawn up, in order to provide reference for industrialized production of Hypsizygus marmoreus.The results showed that several characters including the pH,the soluble protein and total sugar contents, and the activities of carboxymethyl cellulase, xylanase, laccase, manganese peroxidase, amylase had the same trend, when the concentrations of CO₂ were controlled in a medium or low level.When the packet cultivated 120 days under medium concentrations, indicators from the upper, middle and lower parts of package were most consistent than other concentrations.It indicated that maturity of the pack was well.However, under the condition with high concentrations of CO₂,the hyphae metabolism had appeared as anti-reverse disorder.Furthermore, the concentration of CO₂ had an effect on the yield.The results indicated those incubated with a medium level of CO₂ concentration producted the highest yield(520.40 g·bag^-1),and other samples performed smaller package yields, no matter under a low(496.66 g·bag^-1) or high(453.33 g·bag^-1) level of CO₂ concentrations.