Abstract: To elucidate the differences in photosynthetic characteristics among four species of the genus Sinojackia,to understand the ecological adaptability of four species of the genus Sinojackia,and to provide a theoretical basis for the protection and use of rare and endangered plants, the photosynthetic characteristics of two-year-old seedlings of S.microcarpa,S.xylocarpa,S.huangmeiensis and S.sarcocarpa were measured using a Li-6400XT portable photosynthesizer.The results showed that the daily photosynthetic process of S.microcarpa and S.xylocarpa showed “single-peak” curves under strong light in summer, while S.huangmeiensis and S.sarcocarpa showed an obvious “midday depression of photosynthesis” caused by non-stomatal limiting factors.Among the four species, S.microcarpa had the highest daily net photosynthetic rate, maximum net photosynthetic rate and relative chlorophyll content, indicating that S.microcarpa had the best photosynthetic structure and function and the strongest photosynthetic capacity.The photosynthetic capacity of S.xylocarpa was the weakest.Among these four species, S.microcarpa had the highest light saturation point and apparent quantum rate, the strongest light utilization rate and the lowest light compensation point, indicating that S.microcarpa could tolerate both strong light and shade and had the broadest ecological range of light adaptation.S.microcarpa had the highest maximum carboxylation rate, maximum electron transfer rate and triose phosphate utilization rate, indicating the highest CO₂ utilization capacity.In conclusion, S.microcarpa had the highest photosynthetic capacity and CO₂ utilization capacity followed by S.huangmeiensis,S.sarcocarpa and S.xylocarpa.