Abstract:The variation of biomass, vertical distribution and annual dynamics of the fine roots of Hevea brasiliensis in 3 different ages, i.e., immature period （5a）, early yielding period （9a） and peak yielding period （16a）, were studied with the method of sequential root coring. The results showed that the total biomass of the fine roots of H. brasiliensis at 5a, 9a, 16a was 2056.18kg·hm-2, 1557.42kg·hm-2, 1174.90kg·hm-2 respectively, indicative of a close relationship with the tree ages although that of the immature trees was very sensitive to environmental factors as well. About 80% of the fine root biomass of the rubber tree was found present in the soil layer of 0-40cm and the remaining 20% decreasing with soil depth. Some 4 regression models were established for the estimation of the fine root biomass, of which the exponential model gave better results. Comparing of the fine root biomass in different months over the year discovered that the annual dynamics of the fine root biomass of rubber tree showed a double-peak type, i.e., April and August being the peaks for the trees at 5a and 9a while June and October for the trees at 16a, much less responsive to environmental changes. Monthly variation of the fine root biomass in the surface soil layer were different among the trees of various ages, but in the subsoil layer a double-peak pattern was recorded with milder variation in deeper soil.