A light control treatment with three light gradients (100%, 66% and 10% of natural light) was conducted to simulate the light conditions of the forest edge, forest gap and understory where seedlings grow. This was achieved by building shade shelters covered by woven black nylon nets. The purpose of this experiment was to study the morphology, photosynthetic characters, biomass accumulation and allocation of Quercus acutissima and Robinia pseudoacacia seedlings in response to diverse gradients of light. The results showed that morphological features of plant height, stem diameter, total leaf area, crown area, leaf area index and total leaf number were seriously inhibited under severe shade conditions, while moderate shade treatment was suitable to growth of seedlings. Effects of light on allometric trajectories of morphology were small in Q. acutissima but more obvious in R. pseudoacacia as the low light depressed the exponents of functions. With a decrease of light, net photosynthetic rate, transpiration rate and stomatal conductance of Q. acutissima were decreased, while the maximum photosynthetic rate of R. pseudoacacia occurred with moderate shade treatment. Light use efficiency in both species increased when the light intensity was restricted. The water use efficiency was the highest under moderate shade treatment, but lowest under severe shade conditions. The trends of biomass accumulation were consistent with those of photosynthetic parameters. Biomass accumulation in each organ was limited by the deficit of light for Q. acutissima, but the best status of biomass accumulation and allocation for R. pseudoacacia was found under moderate shade treatments. Higher leaf area index and lower root to shoot ratio could increase the capacity of light capture. Also, the total content of chlorophyll increased and Chl a/b decreased with decreasing light intensity. The different strategies of growth and light utilization between Q. acutissima and R. pseudoacacia might reveal, to a certain extent, their status in the succession of deciduous broadleaved communities.