This experiment was carried out by using twelve soybean cultivars from different regions in field con-ditions. We measured light response curves and carbon dioxide response curve using LI-6400 Photosynthesis Sys-tem at flowering stage. The results showed that the reaction of different soybean cultivars was different to light andcarbon dioxide, but the trend is consistent. In low light intensity, the net photosynthetic rate of soybean increasedwith increasing of light intensity. When the light intensity exceeds a certain range, the net photosynthetic rate of soy-bean leaves increased slowly, and there was decreased trend. The net photosynthetic rate of soybean increased withincreasing of concentrations of carbon dioxide in a certain range. The net photosynthetic rate of soybean varietiesfrom different sources decreased when carbon dioxide concentrations over 1000μmol·mol^-1.