Abstract: Net photosynthetic rate (Pn), stomatal conductance (Co), internal CO2 concentra tion (Ci), chlorophyll content and leaf area were measured in leaves of Toona ciliata var. pubescens seedlings grown in pots with various shading and various soil water contents. The resuhs showed as follows: The diurnal variations of Pn were "twin-peaked" curve, and the peak value occurred at 10:00 and 16:00 or so. There was an obvious "midday depression" phenoraenon under full light and middle shading (60%), while it didn’t occur obviously under strong shading (80%). The diurnal variations of Ci were just opposite to Pn under the full light. Photosynthesis was the strongest when water content in soil was sufficient. The decreasing of Cond and even variation of Ci showed that the decreasing of Pn was related to non stomatal restriction factors after 10:00. With the increase of leaf area and chlorophyll content under shading, the leaves of T. ciliata var. pubescens had the higher utilization effi ciency on weak light. The results suggested that the control of soil water content and irradiance might help to promote the growth of T. ciliata vat. pubescens.