Abstract: The biomass and the some leaf characters in the seedlings of two dominant tree species in Dinghushan forests were studied under long-term elevated [CO2] conditions. Potted seedlings of Castanopsis fissa and Schima superba were grown in semiopen top chambers with ambient (350μl·l-1) and superambient (500 μl·l-1) [CO2] under natural light. With increasing [CO2], the total dry matter of whole plant increased by 16.6%～26.6%,and both the ratios of underground to total weight and the root/shoot ratio increased. Whereas, the increase in stem diameter of the basic part and the decrease of plant height were also observed under [CO2] enrichment. In addition, the increase of leaf density, leaf thickness and specific leaf weight were associated with the decline of internal space volume. When expressed on dry weight basis, the contents of total nitrogen, Mg, fructose, glucose and sucrose as well as the N/C ratio of leaf of C. fissa reduced obviously by elevated [CO2], but no obvious change in total carbon, soluble sugar, Ca, P and K was observed.