The Photosynthetic Characterization of some Crops and the Correlation with environmental factors were studied by ¹⁴C tracer. The results indicate that the sunlight illuminant intensity、the temp-erature、the Zinc fertilizer and the nitrogen fixing activity of soy-bean rhizobia effect on the photosynthesis importantly, Photosynthesis of C₃ and C₄ plants are defferent Significantly.