This study investigated population distribution and community structure of microorganisms and related ecological factors in the root layer of 10-, 40-and 90-year old tea plants, respectively.The populations of soil eutrophic bacteria, fungi, actinomycetes and Bacillus were measured by the plate-count method.Soil acidity, organic carbon, total nitrogen and total soluble phenol of the soil increased with the age of tea plants.Populations of microbes in the tea root layer varied with the age of tea plants.Eutrophic bacteria and actinomycetes and total microbes appeared as larger colony-forming-unit in the root layer of 10-year old tea plant, as compared with those of 40-and 90-year old tea plants, which were close each other.The size of fungi in the root layer of 10-and 90-year old tea plants was similar but larger than those in the root layer of 40-year old tea plants.The quantity of Bacillus, in the root layer of 40-year old tea plants was greater than those in the 10-or 90-year old tea plant root layer, with the latter having similar values.Soil microbial biomass carbon in the tea plant root layer increased significantly with the age of tea plants.Simultaneously, a significant correlation was not observed between microbial biomass carbon and total colony-forming microorganisms measured by the plate-counting method.Each of the soil properties including organic carbon, total soluble phenol, total nitrogen and pH, had a significant or very significant correlation with microbial biomass carbon.