Abstract: By using phospholipid fatty acid biomarkers (PLFAs), this paper studied the microbial diversity in the rhizosphere soils of 1-, 6-, and 20-year-old tea trees. In the rhizosphere soil of 6-year-old tea trees, the total amount of PLFAs was the highest, and the PLFAs contents of bacteria, actinomycetes, and protozoa were higher than those in the other rhizosphere soils. The rhizosphere soil of 20-year-old tea trees had a higher content of fungi PLFAs but lower contents actinomycetes and protozoa PLFAs than the other rhizosphere soils, whereas the content of bacterial PLFAs was close to that in the rhizosphere soil of 1-year-old tea trees. In the rhizosphere soil of 20-year-old tea trees, the abundance of several microbial groups participating in soil nutrient cycling declined, while the abundance of several microbial groups with low metabolic capacity increased. As compared with those in the rhizosphere soil of 6-year-old teat trees, the activities of urease, phosphomonoesterase and peroxidase in the rhizosphere soil of 20-year-old tea trees were lower, while the activities of invertase and polyphenol oxidase were higher. In the rhizosphere soils of different planting year tea trees, the PLFAs of different microbial groups were closely correlated to the soil enzyme activities and fertility factors. With the increasing year of tea planting, the microbial community structure in rhizosphere soils changed greatly, reflecting in the decline of microbial diversity and the increase of the microbial groups with low metabolic capacity and adapting to poor soil condition, and the soil quality and the activities of some key enzymes had a larger decrement.