Abstract: Charles-Edwards leaf photosynthesis model includes photorespiration and lightless-respiration, and it is more rational than other models and validated easily by measurement through experimentation. This model is adopted to describe photosynthesis of different cucumber leaves on one vine in sunlight greenhouse and its parameters are estimated by using nonlinear least squares approximation. The data of experiment that has been processed during Apr to Jun 2004 are consistent with the results of the model simulation under the determinated range of PAR. But there are different model parameters among different ages of cucumber leaves that were divided into three age groups. And the photosynthesis rates have distinct differences among the growing 20～30 days' leaves.