Abstract: The photosynthetic characteristic and its relation to eco-physiological factors for poplar tree on beach land along the Yangtze River were studied. The main results were as follows:(1)The changes of net photosynthetic rate(Pn)in a clear day showed a double peak curve,two peak values appear at 10:00 and 14:00;(2)There was a close relation between the net photosynthetic rate and the age of tree. The Pn of two year old trees was more than that of seven-year-old trees;(3)The net photosynthetic rate on different elevations were different. In high elevation the growth condition of poplar is better than that in low elevation;(4)Under different densities,the rates of solar energy utilization were different. Small density or large row spacing is beneficial to rise the Pn. Meanwhile large row spacing and small spacing in the rows is beneficial to rise the rate of solar utilization;(5)The Pn was affected by both ecological factors and physiological factors,related to photon flux density,temperature,relative humidity and transpiration rate.