Taking the fine roots of Cinnamomum septentrionale and Toona sinensis which were planted during early preliminary stage of lowefficiency Cupressus funebris forests transformation in the hilly region of central Sichuan as research objects, while using the unmodified pure C. funebris forest as control, we determined in situ respiration rates by applying a LI8100 soil carbon flux measurement system of the 1st-5th order roots and discussed the relationship among the morphological structure and the nutrient concentration of fine roots and respiration to reveal the structural and functional heterogeneity of fine roots. The results showed that the diameter of fine roots, root length and tissue carbon concentration of C. septentrionale, T. sinensis and C. funebris increased with the roots order increased, while specific root length (SRL), tissue nitrogen concentration and specific root respiration rate (SRR) reduced. And species, root order and their interactions showed that the morphology, nutrient concentrations and SRR of these three species fine roots were highly significant effect (P<0.01). Regression analysis indicated that three species SRR of these three species fine roots altered as diameter, SRL and tissue nitrogen concentration changed, which explained the variation with 64.7%, 87.6% and 67.6% of SRR, respectively. These results suggested that there was a close link among morphological characteristics of fine roots, the chemical contents and physiological functions, which provided an important basis to understand the structural and functional variation of plant roots.