Aimed at the decrease of the crop yield caused by drought stress, this paper focused on the physiological ecological characteristics of soybean. The variations of soybean leaf chlorophyll,leaf area,photosynthetic rate,yield and quality are studied through control dry time and varying degrees of soil moisture treatments from the stage of flowering. The results show that the physiological and ecological characteristics of soybean will drop if the dry time is longer and it has recovery trend when the soybean is irrigated timely in a short period of drought time. The chlorophyll content and leaf area are maximum when the soil moisture content is 40% to 50%, and when soil water content is lower than 30%, they are minimum. The photosynthetic rate under control group is higher than that in time and water treatments, and the value of photosynthetic rate will increase if stop the processing. The yield of soybean will reduce with longer time stress and lower water stress, but the grain weight is contrary. The protein content will increase and the fat content will decrease.