[Objective] To explore the effects of different irradiances on the photosynthetic characteristics of invasive plant Bidens frondosa and native species Lactuca indica, and to provide reference for revealing the invasion mechanism and control of Bidens frondosa. [ Method ] The differences of photosynthetic characteristics of two species leaves under 100 % (I1), 40 % (I2), 24 % (I3) and 14 % (I4) irradiances were compared. [ Results ] (1) According to the fitting parameters of light response curves, under 100% irradiance, the maximum net photosynthetic rate (Pmax) and light saturation point (LSP) of B. frondosa were significantly higher than that of L. indica, while the light compensation point (LCP) was lower than that of L. indica. Under 14 % irradiance, LSP was higher than that of L. indica, while LCP and dark respiration rate (Rd) were significantly lower than that of L. indica. The respiration efficiency (RE) of B.frondosa was significantly higher than that of L.indica under different irradiances. It showed that B.frondosa had a wider range of adaptation to irradiances. (2) Under the lowest (14%) and highest (100%) irradiances, the chlorophyll content of B.frondosa was significantly higher than that of L.indica, and the carotenoid content of B.frondosa was significantly higher than that of L.indica under 100% irradiance. (3) According to the fitting parameters of CO2 response curves, the carboxylation efficiency (CE), the maximum carboxylation rate of Rubisco (Vc max) and the maximum regeneration rate of RuBP (Jmax) of B.frondosa were significantly higher than that of L.indica under 100 % irradiance. Under 14 % irradiance, the CE value was lower than that of L.indica, and the Vcmax was significantly higher than that of L.indica. Under 100 % light intensity, the photorespiration (RP) of L. indica without CO2 was higher than that of L. indica, while Rp decreased under medium and low light intensity, which was lower than that of L. indica. (4) Pmax, Rd, CE, Amax, Rp and Jmax of B.frondosa had higher plasticity than that of native species L. indica, while the RE value and carotenoid content of L. indica had higher plasticity. [ Conclusion ] Under different irradiances, invasive species B.frondosa showed higher photosynthetic capacity and photosynthetic physiological plasticity, and showed stronger adaptability to light heterogeneity. These characteristics would enhance the invasiveness of the invasive species B.frondosa, and contributed to its invasion.