Abstract: In order to reveal the mechanism of biological fermentation further and provide theoretical references for the establishment of the standard system of organic compost maturity, a high temperature and aerobic composting experiment was conducted by using tobacco stalk as raw materials. The temperature of materials and the activities of main hydrolases and oxidases during fermentation were measured. The results showed that the activities of main hydrolases and oxidases increased gradually during pre-fermentation, but became stable or decreased thereafter. In treatment with microbial agents added, the activities of hydrolases and oxidases were generally higher in the medium of the fermentation and the peak time appeared earlier. But the activities of hydrolases showed little difference while the activities of oxidase were much different in the end of the fermentation. The increase in activity of enzymes promoted the metabolic activity of the fermentation, increased the temperature of the pill and speed up the maturity of compost. The activities of pectinases and alkaline phosphatases were more stable in the late period of the fermentation, which could be used as index of compost maturity.