Abstract: The photosynthesis physiology and canopy location, microclimate factors of tomato were analyzed systematically in the greenhouse in spring in southern part of China, based on the data collection by the advanced instruments of LI-6400 photosynthesis measuring system and hand-carried automatic weather station. There was a great difference of net photosynthesis rate for different canopy locations. The phenomenon, Noon recess, appeared obviously at noon in the green house. The predominated factors are irradiation and temperature. The nonlinear equation was fitted in terms of photosynthesis rate and photo synthetically active radiation. The results are useful to environment regulation in the similar greenhouse.