Abstract: Liriodendron chinense is a common deciduous tree.Its net photosynthetic rate(Pn),gross chlorophyll content,chlorophyll a and b content in different growth seasons and different positions within tree crown were determined.The correlativity between net photosynthetic rate and environmental factors and the influence of positions within tree crown on Pn were analyzed. For Liriodendron chinense,the gross chlorophyll content showed flourishing stage>final stage>initial stage,which accorded with the seasonal change of the net photosynthetic rate.And photons density was the major influencing factor of Pn in initial stage and final stage of growth season,while temperature was the major influencing factor in flourishing stage.The daily course of Pn was single peaked in initial stage and final stage,unobvious double peaked in flourishing stage.The influence of positions within tree crown on net photosynthetic rate was not notable in different growth stages.