Abstract: The paper aims to explore the photosynthetic capacity of Populus euramericana cv‘. Hongxia’. The author measured the photosynthetic indexes of Populus euramericana cv.‘Hongxia’by Li- 6400 portable photosynthetic meter, plotted the light response curve and the diurnal variation map of photosynthetic index, and fitted and calculated the light response curve by modified rectangular hyperbola, compared with the Populus spp and Populus euramericana cv‘. Quanhong’. The results showed that: from the perspectives of the line distribution position, the light compensation point (LCP), light saturation point (LSP), apparent quantum yield (AQY), maximum net photosynthetic rate (Pnmax) and net photosynthesis rates (Pn) under the same light intensity, the photosynthetic capacity of Populus euramericana cv‘. Hongxia’was poor, and it was not as good as that of the similar trees Populus spp and Populus euramericana cv‘. Quanhong’; the diurnal variation curves of the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductivity (Gs) and stomatal CO2 concentration (Ci) were relatively stable with no obvious peak value, and the response to light stress was weak and the self-regulation ability was poor.