The project conducted a potculture method to study the effect of Cupressus funebris root exudates on the growth of Koelreuteria paniculata fine roots in mixed forests. Four experiment groups of G1, G2, G4 and G8 were set up and separately added the potted seedlings of K. paniculata, followed by treatment with root exudates of 1, 2, 4, and 8 cypresses respectively, which investigated the effects of that root exudates on fineroot morphology, N and P contents in orders 1-5 roots. The results showed that: (1) fineroot diameter increased with root order increasing. Root exudates significantly reduced fineroot diameter in orders 1-2. Specific root length and specific root surface area decreased while root order increasing. Root exudates significantly increased specific root length and specific root surface area in orders 1-2. With the increasing concentration of root exudates, specific root length and specific root surface area increased firstly, while the diameter decreased firstly, followed by all of them tended to be stable. (2) Contents of N and P decreased with the increase of root order, but the change of N/P in root order was not obvious; root exudates significantly increased N and P contents in fineroot orders 1-2, but decreased N/P in orders 1-5; with the growing concentration of root exudates, fineroot P content increased, N/P decreased, and N content increased primarily and then remained no change. (3) Contents of N and P in fine roots were remarkably correlated with the morphological characteristics. Root exudates could improve the availability of soil nutrients, thereby alleviating the symptoms of P deficiency in plants. Fine roots could enhance nutrient use efficiency through adjusting their morphology. Meanwhile, root exudates mainly affected morphology and contents of N and P in fineroot orders 1-2. The results indicated that root exudates from 4 strains of C. funebris were more beneficial to the growth of K. paniculata.