Abstract: The paper aims to study the growth promotion action on woody plant induced by Trichoderma asperellum 650. Taking tissue-cultured Shanxin poplar (Populus davidiana×P. alba var. pyramidlis) seedlings transplanted into pots as the material, the effects of the addition of T. asperellum 650 conidia onto the root at T (5×10³ cfu/cm³ soil) concentration on the growth and photosynthetic characteristics of seedlings were studied. The results showed that the average plant heights, base diameters and biomass yield of T group were all significantly higher than those of CK (P<0.05). The net photosynthetic rate (Pn) curves of T and CK groups were both single-peaked and the peak values were achieved at the time point of 12:00. The Pn of T remained significantly higher than that of CK throughout the duration of 10:00-14:00 (P<0.05). On the other hand, the stomatal conductance and transpiration rate of T also remained significantly higher than those of CK (P<0.05) except for the time point of 8:00. Although T showed significant difference from CK in the daily intercellular CO₂ concentration at the time points of 8:00 and 12:00 (P<0.05), the trends of its changes still coincided with that of CK. What’s more, the maximum net photosynthetic rate, light saturation points and apparent quantum efficiency of the poplar seedlings all exceeded those of CK after T. asperellum 650 induction. All the above results indicated that T. asperellum 650 induction significantly improved the photosynthetic efficiency of the Shanxin poplar thus promoted seedling growth.