The combination of soluble polysaccharide and black soybean protein could change many functional properties of protein. In this experiment， black soybean protein was mixed with soluble polysaccharide with different time of ultrasonic treatment， which had the effect on physical properties and structure. The results showed that the stability of emulsification and emulsification was the best when the soy protein isolate was mixed with soluble polysaccharide at the ratio of 1 ∶ 2. When treated the compound of 1 ∶ 2 with ultrasonic， the emulsions of the composites treated for 16 min were the best， and the emulsions with 8 min were the best. Meanwhile with the prolongation of ultrasonic time， there was an increase in the α-helix and a decrease in the β-sheet， which indicated the structure and functional properties of proteins were closely related to each other. Therefore， proper ultrasonic treatment can influence the degree of compounding of soy protein isolates with soluble polysaccharides， and improved some properties.