Abstract: Growth and photosynthetic properties of Sonnerratia apetala seedlings were studied under different light intensity environments according to light intensity of Sonnerratia apetala in field.The results indicated that with the light intensity lessening,the trend of growth and photosynthetic properties of Sonnerratia apetala seedlings decreased.The difference of different treatments was significant.When the light intensity was 80% and 40% of full light,the growth of seedlings became worse,they grow worse than that of full light.The weak light environment was beneficial to stem height,leaf area and ratio of length to width of lamina only in initial shading stage(2 to 4 months),but with the shading time prolonging,the growth of seedlings appeared to the trend of decline.The growth of seedlings were restricted seriously in initial shading stage when the light intensity was 20%.The death rate of seedlings of Sa80,Sa40 and Sa20 in shading treatment 180 days were 42%,70% and 100%,respectively.Biomass of root,stem and leaf were decreased by about 90%,80% and 91% in weak light intensity environment.With the light intensity lessening,the trends of physiology parameters such as chlorophyll contents,net photosynthetic rate decreased,the difference among them was significant.Therefore,weak light intensity environment was the main reason for lower growth rate,lower photosynthetic rate and higher death rate of Sonnerratia apetala seedlings.In addition,the natural regeneration and diffusion and the artificial forestation technique of Sonnerratia apetala seedlings were discussed.