Abstract: Aleaf model was est ablished for simulating phot osynthesis of winter wheat based on charact eristics of physiological ecology of plant,and then a canopy photosy nthesis model was scrolled up from the leafmodel.The influence of CO2,O3 and spectrum variation on canopy photosynthesis was fully considered in the model.Validation of the leafmodel showed that the model could simulate photosynthesis rate of winter wheat in field fairly well.The simulation result by using the model indicated that:(a) When the concent ration of O3 increased from 0×10-9V/V to 200×10-9V/V,the canopy photosynthesis will decrease about 29% in contrast with the base value.The canopy photosynthesis will enhance about 37% when the concentration of CO2 changed from 330×10-6V/V to 660×10-6V/V.The canopy photosynthesis declined with the debasement of spectrum coefficient according to the linear relation,which reduced about 27% with the spectrum coefficient varied from 0.5 to 0.4.(b) The canopy photosynthesis will be reduced about 35% in suburb,when the spectrum coefficient reduced to 0.4 and the concentration of O3 increased to 200×10-9V/V,even with a doubled CO2 concentration and unchanged climatic scenarios.