This study aims to investigate the seasonal changes of soil carbon and nitrogen-transformed enzyme activities and their driving factors in successive rotations of subtropical Chinese Fir (Cunninghamia lanceolate) plantation. The results would provide basis for assessing nutrient cycling and soil quality in forest. Through canonical redundancy analysis (RDA) the relationships between soil physical properties, nutrient conditions, and enzyme activities were analyzed in different generations of Chinese fir plantation (FRP, SRP, TRP) and Castanopsis Kawakamii forest (NF) in Fujian province, China. A significant decrease of soil pH was observed in Chinese fir plantation compared with NF, but no significant changes were found between FRP, SRP, and TRP. In December, there was no significant difference on soil total carbon and nitrogen among different generations of Chinese fir plantation, and the SRP and TRP were significantly higher than the NF (P<0.05). In June, soil total carbon of TRP was significantly higher than that of FRP (P<0.05), but not significantly different from that of SRP and NF. In December, there was no significant difference on soil NH₄⁺-N and NO₃^--N among different generations of Chinese fir plantation. In June, soil NO₃^--N of FRP was significantly higher than that of SRP and NF (P<0.05), but not different from that of TRP. Soil urease activity of NF was significantly higher than that of FRP, SRP, and TRP, but no significant difference was found among FRP, SRP, and TRP in December. Soil asparaginase activity of FRP, SRP, and NF were significantly higher than that of TRP (P<0.05), but no significant difference was found among FRP, SRP, and NF. The RDA showed that soil moisture, NO₃^--N, and pH made significant contributions to variations of soil enzyme activities, especially positively related to the activities of soil asparaginase, β-glucosidase (BG), and protease, but negatively related to soil N-acetyl-β-D-glucosaminidase (NAG). The soil physiochemical properties and enzyme activities in mature and over-mature Chinese fir plantations recovered to different degrees compared with the natural forest, and their variations were largely influenced by the seasonal changes. Additionally, a long-term observation on soil enzyme activities in response to the environmental changes is recommended.