Soil enzymes, which were secreted by soil microorganisms, play important role in soil nutrients cycles through mediating the degradation, transformation and mineralization of soil organic matter. And soil aggregate structure can affect the soil enzyme activities by influencing microbial activities and accessibility of soil organic matter. Thus, study of soil enzyme activities on an aggregate level could provide insight into nutrient cycling and could also be used as sensitive indicators for soil fertility. Pinus massoniana Lamb., as the top 5 plantation species in China, is also the main vegetation type with key ecological and economic importance in the Three Gorges Reservoir Area, China, but the productivity of P. massoniana forests is low due to extensive management. Quantifying the enzymatic activities within soil aggregates in P. massoniana forests could provide basic data for forest managements in this area. Hence, in this study, we chose two typical mixed P. massoniana plantations in the Three Gorges Reservoir area, P. massoniana and Cunninghamia lanceolata mixed plantations (MS) and P. massoniana, C. lanceolate and Quercus mixed plantations (MH), as the objects. The soil samples in top 10 cm were collected from six 20 m×20 m plots (three plots in each mixed plantation) to test distribution of soil aggregate (i.e. large macroaggregates (> 2 mm), small macroaggregates (0.25-2 mm), and microaggregates (< 0.25 mm)) through modified dry-sieving method, and to analyze the activities of 5 hydrolases (i.e. soil β-glucosidase, cellobiohydrolase, N-acetyl-glucosaminidase, acid phosphatase and leucine aminopeptidase) and 2 oxidase (phenoloxidase and peroxidase) within soil aggregates. The relationships between soil enzymes activities, soil nitrogen, soil organic carbon, soil total phosphorus and soil carbon to nitrogen ratio within aggregate were also observed. The results showed that: 1) the distribution of soil aggregates significantly increased as the aggregate size increased in both two mixed plantations, and the proportion of large macroaggregates was the highest, which accounting for 60% in the soil. The distribution of small macroaggregates was significantly higher in MS (39.53%±1.65%) than that in MH (32.24%±2.51%) but no significant differences were found in other two aggregate sizes. 2) The activities of 5 hydrolases, soil organic carbon and soil total nitrogen were higher in microaggregates than those in other two aggregates, while the activities of 2 oxidase were highest in large macroaggregates in both two mixed plantations. 3) The activities of cellobiohydrolase and leucine aminopeptidase, geometric mean of soil enzymes activities and soil carbon to nitrogen ratio in large macroaggregates and microaggregates were significantly higher in MH than those in MS, and variation of soil nitrogen within soil aggregates attributed to the significant differences of soil enzymes discussed above. Our results indicated that Quercus in MH improved the enzymatic activities within soil aggregates and was beneficial to improvement of soil fertilities in the study area.