Abstract: The author investigated the characteristics of photosynthesis of damaged poplar leaf and discussed the photosynthesis compensation of poplar after larvae of Micromelalopha troglodyta feeding. The results showed that the diurnal variation of net photosynthetic rate (Pn) of poplar leaf appeared a single peak curve after damaged by M. troglodyta and the aptitude was much higher than that of CK. Meanwhile, the Pn peak appeared at 12:00 a.m., which delayed two hours and the Pn peak value was 16.4 % higher than that of CK. The CO2 accumulation of damaged leaf per unit area were 9.6 % higher than that of CK at 8:00 to 12:00, and very little decrease occur at 13:00 to 18:00. However, the value of Pn accumulation had no obvious difference in the whole day (8:00-18:00) between CK and the damaged leaf (p>0.05). The diurnal change of transpiration rate (Tr) showed a doublepeak curve, the peak appeared at 12:00 and 15:00 . Tr and the diurnal accumulative transpiration water quality of the damaged leaf were obviously lower than those of CK. However, the water utilization efficiency (WUE), light saturation point (LSP) and maximum net photosynthetic rate (Pn,max) of the damaged leaf were significantly increased (p＜0.05) compared to CK, especially the dark respiration rate (Rd) was 10.33 % higher than that of CK. But there was no significant difference in apparent quantum yield and light compensation point (LCP) between damaged leaf and CK. Our study indicated that poplar had developed a adaptive mechanism of photosynthesis compensation to the damage of M. troglodyta