Larix principis-rupprechtii was introduced in Shaanxi Province more than 50 years ago, and most of these trees were planted in the Qinling Mountains. In order to study the fertility of soil in different-aged Larix principis-rupprechtii plantations in this area, we chose young- (5 and 10 years old), middle- (20 years old), and near-mature- (30 and 40 years old) aged Larix principis-rupprechtii plantations in the Nantan Nursery Garden of Taibai and Huoditang of Ning-shan in Shannxi Province as the experimental sites, and established three 20 × 20-m plots in each age stand plantation in 2012. In each plot, soil samples were collected from three depths (0-20 cm, 20-40 cm, and 40-60 cm) at five randomly located points. Using these samples, we examined the soil chemical properties (pH, organic matter, available N, available P, and available K) and enzyme activities (phosphatase, urease, invertase, and catalase) in the different-aged plantations. Soil pH in the 0-20-cm layer decreased from 6.71 in the 10-year-old plantation to 5.72 in the 40-year-old plantation; however, with an increase in soil depth there was a slight increase in pH. Soil organic matter and available nutrients in near-mature plantations were significantly higher than those in the young plantations (P<0.05). The variation ranges of these soil properties in the 0-20cm layer were as follows: organic matter, 10.12-23.12 mg/kg; available N, 27.82-142.82 mg/kg; available P, 1.91-2.53 mg/kg; and available K, 104.33-264.67 mg/kg. There were significant reductions in soil organic matter and available nutrients as the soil depth increased (P<0.05). With an increase in plantation age, the activities of soil phosphatase, urease, invertase, and catalase showed a "high-low-high" tendency. In the 0-20cm soil layer, the variation ranges for these activities were as follows: phosphatase, 28.06-53.93 mg/100 g; urease, 0.31-0.65 mg/g; invertase, 6.04-68.42 mg/g; and catalase 1.39-4.61 ml. The activities of these four enzymes conspicuously decreased in the 20-60cm layer (P<0.05). The activity of invertase in young plantations was significantly higher than that in the near-mature plantations, whereas for the other three enzyme activities, the converse was true. Correlation analysis indicated that soil pH was significantly negatively related to soil organic matter, available N, available P, and catalase activity. This suggested that the efficacy of soil nutrients increased as soil pH decreased, and that catalase promoted this effect. Phosphatase activity was highly significantly positively related to soil organic carbon and available N, P, and K (P<0.01), indicating that soil phosphatase increased the contents of soil available N and K, whereas it accelerated the decomposition of organic P. There were highly significantly positive correlations between urease activity and organic matter and available N, P, and K. In this respect, urease had the same effect as phosphatase. This study indicated that because of the lack of soil available N and available P in this area and the rapid growth of plants, the fertility of plantations in the Qinling Mountains until Larix principis-rupprechtii reaches an age of 20 years. With a further increase in plantation age, however, soil enzyme activities increased as organic matter, which provides zymolyte for soil enzymes, accumulated. This provided more available nutrients for Larix principis-rupprechtii and improved soil fertility. Accordingly, on the basis of these findings, we suggest that fertilizer should be applied to soil until Larix principis-rupprechtii plantations reach 20 years of age in order to avoid nutrient limitation for plant growth.