Abstract: Different age-level typical sample plot are selected according to the distribution status, which means the distribution weight among each cities and countries of Cunninghanua lanceolata, pinus massoniana lamb and eucalyptus. These sample plots are young growths, immature timbers, near-mature forests, mature forest and overmature forests. The area of sample plot is 20m*50m, the surface soil samples (0cm-10cm) were collected by using grid module method. The microbial amount was detected by using diluted flat smearing method, and the microbial biomass was measured by using chloroform fumigation.The result shows:the bacterial amount is absolute dominance among the cultivatable soil microbes of the three plantations in all age stages. The microbial amount of young growth, immature timber and overmature forest present a downwards order as:Cunninghamia lanceolata >eucalyptus >Pinus massoniana Lamb. The microbial amount of Cunninghamia lanceolata young growth, Pinus massoniana Lamb and eucalyptus near-mature forest are the biggest of the three forest types in all age stages. The microbial carbon (Cmic) of Cunninghamia lanceolata young growth, Pinus massoniana Lamb immature timber and eucalyptus overmature forest are the biggest. The microbial nitrogen (Nmic) of Cunninghamia lanceolata overmature forest, Pinus massoniana Lamb and eucalyptus young growth are the largest. The microbial phosphorus (Pmic) of Cunninghamia lanceolata mature forest, Pinus massoniana Lamb young growth and eucalyptus near-mature forest are the biggest. The Cmic, Nmic and Pmic of Cunninghamia lanceolata plantation present trends that decrease first and then increase as the age of forest varies. There is no obvious principles of the microbial biomass of Pinus massoniana Lamb and eucalyptus plantations as the forest age varies. There is significant fractal relationships between soil Nmic and soil bacterial and fungal amount(P<0.05), and there is no fractal relationship between the rest of microbial biomass and microbial amount.