Abstract: Rhizosphere is the zone of soil surrounding a plant root, which provide a conducive special environment for a wide range of microorganisms. Root secretions at different plant growth stages provide nutrition and energy for microorganisms, thereby notably influencing their number, composition and activity. Metabolism of microorganisms in the rhizosphere promotes or limits plant nutrient absorption and growth, and also influences the transformation of substances in rhizosphere soil. Tripterygium wilfordii Hook. f. has well-developed root systems, and is frequently planted along with other trees. This makes the study of rhizosphere microorganism activity very important for soil fertility and growth of T. wilfordii. This paper used three different T. wilfordii forest stands mixed Cunninghamia lanceolata (Lamb.) Hook (Chinese fir) and T. wilfordii forest, mixed Magnolia officinalis Rehd. et Wils. and T. wilfordii forest, and natural T. wilfordii forest) in Taining County, Fujian Province as experimental materials and the dilution-plate technique to determine the number of bacteria, fungi and actinomyces in rhizosphere and non-rhizosphere soils. The results showed that: the number of rhizosphere microorganisms was much larger than non-rhizosphere microorganisms. In the three forest stands, the number of microorganisms in either rhizosphere or non-rhizosphere soil was in the order of: bacteria > actinomyces > fungi. Rhizosphere microorganisms were more active than non-rhizosphere microorganisms. In three forest stands, rhizosphere to non-rhizosphere ratio of microorganisms number was higher than 1. The activity of microorganisms in the three forest stands was in the order of: mixed M. officinalis and T. wilfordii forest > mixed Chinese fir and T. wilfordii forest > natural T. wilfordii forest. This suggested that mixed forest modes enhanced the activity of microorganisms.