Soil microorganisms play an important role in nutrient cycling in forest ecosystems, so it is important to investigate the changes in soil microorganisms with forest age. We collected soil at different soil depths (0-10 cm, 10-20 cm, and 20-30 cm) to investigate the microbial phospholipid fatty acids (PLFAs) and the effects of soil properties and plant diversity on soil microbial PLFAs. The results showed that: (1) with the increase of forest age, the total PLFAs, fungi, and bacteria content of the 0-10 cm soil layer showed a decreasing, increasing, and then decreasing trend. (2) Soil fungi and bacteria showed significant correlations with soil organic carbon, pH, available phosphorus, nitrate nitrogen, available nitrogen, total nitrogen, β-glucosidase activity, acid phosphomonoesterase activity, phenol oxidase activity, peroxidase activity, and microbial biomass phosphorus. (3) The total PLFAs, fungi, and bacteria contents in the 0-10 cm soil layer were higher than those in the 10-20 cm soil layer and the 20-30 cm soil layer. It should also be noted that the microbial PLFAs declined as the stand age increased to 10 years, and fertilizers should be reasonably applied to improve soil fertility in future C. hystrix plantation forest management.