The effects of CO2 density for ventilation on daylily vegetable MA storage in small plastic bag were carried out under 0～1℃.(1)The single index of CO2 showed the best treatment was 14%～16%(3 levels of CO2 density 8%～10%、11%～13% and 14%～16% were compared in ventilation),and good flower rate was kept 94.34% and 81.94% after harvest 30 days and 40 days respectively.(2)The double index experiment was performed with CO2 density 22%～24% or 26%～28% first and then reduced to 14%～16%.The results showed the optimum treatment with 22%～24% CO2 density first had the best good flower rate to 99.85 % and 86.32% after harvest 40 days and 50 days respectively.