Abstract: In order to research the photosynthetic characteristics effect of different bred years soybean varieties in heilongjiang province, 5 representative soybean varieties bred in 1985-2005 years as the test materials and seted mild-stress(the field maximum water-holding capacity 55-60%), serious- stress(the field maximum water-holding capacity 35-40%) and normal(the field maximum water-holding capacity 75-80%) in flowering period to analysis the photosynthetic characteristics. The results show that the leaf area per plant, leaf color value, net photosynthetic rate and grain weight per plant of different bred years soybean varieties present decline trend as the drought intension enhance and exist differences. Under the drought stress conditions and as varieties bred time goes on, the leaf area per plant, leaf color value, net photosynthetic rate and grain weight per plant present a general trend increased firstly and then decreased and associated with the bred years reached a extremely significant level except the leaf area per plant under serious- stress conditions. From the variation trend of the leaf area per plant, leaf color value, net photosynthetic rate and grain weight per plant and as the varieties genetic improvement, the drought resistant ability of different bred years soybean varieties in heilongjiang province show a general trend decreased firstly and then increased.