Increasing levels of atmospheric CO₂ and temperature are the two most important factors of global climate change. As two key environmental factors for plant growth, the changes in atmospheric CO₂ concentration and temperature can affect photosynthetic productivity of crop plants. Moreover, used as a raw material in plant photosynthesis, increasing atmospheric CO₂ concentration will have a direct positive impact on photosynthesis and a series of physiological and biochemical process in plants and finally on crop yield. The atmospheric CO₂ level is increasing sharply with the expanding scope of human economic activities, which raises Earth surface temperature, eventually leading to global warming. In general, the photosynthetic rate is not saturated in most crop species under ambient CO₂ level (about 375 μL/L); hence, the increasing atmospheric CO₂ level can enhance the photosynthetic rate in most crop plants. Howerver, the effect of climate change on photosynthesis, and physiological and biochemical processes is much more complex and unknown in most crops, especially in cultivars with high photosynthetic efficiency under the assumption of concomitant global warming and atmospheric CO₂ concentration increase. In this study, soybean cultivar HN41 with high photosynthetic efficiency ( ≥ 17.64 μmol [CO₂] m^-2s^-1) and three varieties ZD16, ZD35, and GHD2 with normal photosynthetic efficiency (10.75-15.48 μmol [CO₂] m^-2s^-1) were selected to study morphological traits and yield of soybean under elevated levels of CO₂ (650 μL/L vs. ambient CO₂) and temperature (± 0.5-0.6℃ vs. ambient temperature). The results indicated that CO₂ levels significantly affected plant height and stem diameter, as well as dry weight and seed weight per plant. Temperature levels and the interaction between CO₂ concentration and soybean cultivars significantly affected seed weight per plant. Relative to ambient CO₂ concentration, elevated levels of CO₂ promoted plant height, stem diameter, and dry weight and seed weight per plant, particularly under higher temperature. Moreover, elevated CO₂ significantly increased plant height in HN41, ZD16, and GHD2 at high temperature (18.9%, 24.4%, and 31.5%, respectively) and significantly enhanced dry weight per plant in HN41, ZD16, ZD35, and GHD2 at ambient temperature (7.3%, 4.7%, 16.0%, and 18.8%, respectively), in contrast to ambient CO₂ levels. Compared with ambient temperature, higher temperature significantly increased only the stem diameter of HN41 under elevated CO₂ levels and significantly enhanced the grain weight per plant in HN41 under ambient CO₂ levels. In addition, stem diameter, root/shoot ratio, and grain weight per plant in HN41 were significantly greater than those in normal cultivars (ZD16, ZD35, and GHD2) under the same conditions of atmospheric CO₂ levels and temperature, whereas dry biomass per plant in HN41 was significantly increased compared with that in ZD16 and GHD2. In conclusion, increase of both atmospheric CO₂ levels and temperature significantly affected plant growth of the highly photosynthesis-efficient soybean. Elevated CO₂ concentration can promote plant growth particularly at high temperature, whereas elevated CO₂ favors accumulation of photosynthetic products at ambient temperature especially for the highly photosynthesis-efficient soybean.