The effect of different temperatures, relative humidities, and packaging materials on cured tobacco leaves mildew was investigated in laboratory at 20, 30 and 40 ^oC, and at 65, 75, 85 and 94% relative humidity respectively. Two types of common packaging materials, kraft paper and high-density polythene film, were tested. The cured tobacco leaves mildew degree developed significantly with increasing relative humidities at 30 ^oC. The cured tobacco leaves quality could be kept well at 65% relative humidity. However, the severe spoilage rapidly appeared after 3 d and 6 d exposure at 94% relative humidity, respectively. Different temperatures had significant effect on the cured tobacco leaves mildew at 75% relative humidity. The cured tobacco leaves mildew happened after 11 d and 3 d of exposure time at 20 ^oC and 30 ^oC, respectively. The favorable temperature for mould development is 30 ^oC, and the cured tobacco leaves mould could not developed during the whole exposure time at 40 ^oC. Kraft paper pouches were better than high-density polythene film pouches for keeping the cured tobacco leaves from mildew during the whole exposure time. These results suggested that the cured tobacco leaves mildew could be prevented by rationally controlling environment condition.