Twelve species of shade plant were used to study the photosynthetic characteristics under sun-shading conditions.The net photosynthetic rate change,average net photosynthetic rate,apparent quantum yield and light compensation point was investigated under different sunshading conditions.The results showed that the photosynthetic characteristics changed under different shading treatments.When the sun light was weak,the net photosynthetic rate varied from a two-peak curve to a single-peak one,which only happened under a certain sun-shading degree.With the increase of sun-shading degree,the daily average net photosynthetic rate and the apparent quantum yield increased to a peak,and then fell down while the light compensation point decreased continuously.There were extremely significant differences for each index of photosynthetic characteristics among 12 species of shade plant under different sun-shading treatments.Proper sun-shading is beneficial to the growth of shade plant and improvement of photosynthetic characteristics.