【Objective】Soil microbes, as an active component of the soil, play an essential role in the forest ecosystem. It is, therefore, of great significance to study characteristics of the soil microbial community structures in plantations different in evolution process to evaluation of dynamics of soil quality and maintenance of soil microecological balance in the plantations. 【Method】In this paper, evolution of the soil microbial community structure and soil metabolic function diversity with age (13 a, 25 a, 38 a and 58 a) of Pinus massoniana plantations in subtropical China was explored using the phospholipid fatty acid（PLFA）method and BIOLOG technique. 【Result】Results show that bacteria were the dominant soil microbe, fungi and actinomyces followed in dominance, and protozoa did in the end in the soils of the plantations regardless of age; in terms of soil microbial total PLFAs, fungal population and fungal/bacteria, the plantation 13 a in age ranked first and that 38 a in age in the end, while in terms of soil biomass of bacteria, gram-positive bacteria (G⁺), gram-negative bacteria (G^-) and actinomyces, the plantation 25 a in age ranked first．Hierarchical clustering and principal component analysis (PCA) revealed that stand age did affect soil microbial community structure significantly, and as a result, soil microbial community structure in the plantations 13 a and 25 a old differed sharply from those in the plantations 38 a and 58 a old. Redundancy analysis (RDA) of soil PLFAs and soil nutrients shows that soil organic carbon, total nitrogen and pH were the main factors affecting soil microbial community structure. In the light of average well color development (AWCD) and microbial functional diversity indexes of the soil (Shannon indexes、Simpson indexes and McIntosh indexes) the plantations displayed an order of 25 a > 13 a> 58 a >38 a; the plantations also varied sharply in utilization of carbon sources. Amino acids, carboxylic acids and amines were the main carbon sources in all the soils, and the plantation 25 a old was the highest in utilization rate of these carbon sources. 【Conclusion】 Both the PLFA and BIOLOG demonstrate that when the plantations of Pinus massoniana grow over 25 years, their soil microbial community structures lower in stability and their metabolic function does in activity, too significantly, which in turn exacerbates microecological imbalance in the soils of Pinus massoniana plantations.