Soil microbes , soil enzyme activity and soil biochemical action intensity in the stands of the broadleaf forest and Cunninghamia lanceolata stand of the first , the second , the third planting were studied comparatively. The results indicated that , through the substitution of Cunninghamia lanceolata plantation ( the first planting) for broad-leaf forest and then the continuously planting Cunninghamia lanceolata , the total quantity of major soil microbes declined , of which the first rotation of Cunninghamia lanceolata was decreased by 59. 88 % in the top soil (0～20 cm) compared with that of the broadleaved forest , and that of the second and the third rotation was of 14. 68 % , 16. 51 % respectively compared with that of the first rotation. The proportion of bacteria and fungi in the amount microbes increased , while that of actinomyces decreased. The amount of major physiological group including ammonifiers , nitrogenfixing bacteria , cellulosedecomposing microbes , aerobic nitrogen fixing bacteria and anaerobic nitrogen fixing bacteria all decreased. The activity of soil enzyme weakened which include invertase , urease , proteinase , acid phosphtase , catalase and perxidase. Soil biochemical action activity impared which include ammonification , nitrification , nitrogen fixation , and decomposition of cellulose. As to the soil respiration , the release amounts of CO₂-decreased , while the RQ value increased. All of which may led to the degradation of the soil fertility.