Abstract: Proteins are widely used in food ingredients because of their excellent nutritional and functional values. We investigated the effect of ultrasound on the functional properties of different ratios of soybean-whey mixed protein. In the experiment, we used soy protein and whey protein as raw materials, use the particle size, ζ-potential, endogenous fluorescence spectrum, their indices from scanning electron microscope, as well as the emulsification activity, emulsion stability, texture, water holding capacity were studied for physico-chemical properties and functional properties. The results showed that when the mass ratio of SPI-WPI mixture was 5:5, the emulsification activity and emulsion stability reach highest (65.5 m2/g, 16.3min), and the particle size distribution changed from double peak to single peak, the volume average particle size reached the minimum value (205.6 nm), and the absolute value of the ζ-potential reached the maximum (21.4 mV), the mixed system had the best stability at this time. The endogenous fluorescence spectrum showed that fluorescent substances released and the fluorescence intensity continued increasing, which indicated the protein structure of the mixed system was changed in ultrasonic treatment. After ultrasonic treatment, the mass ratio of mixed protein at 5:5 had the best gel properties, the highest hardness (475.61N) and the maximum water holding capacity (85.32%), the gel has a dense network structure, consistent with the results of the scanning electron microscope, which indicated the gel structure of the mixed protein system was uniform. In recent years, mixed proteins foods are more conducive to human health and have been acquired new texture, especially the mixture of plant proteins and animal proteins, which have received increasing attention. Whey Protein Isolate (WPI) and Soy Protein Isolate (SPI) are widely used in the food industry. However, the application of expanded protein in food and non-food field has been limited by poor gelation of WPI and poor emulsification of SPI, which lead to seriously restrict to the application of mixed protein in food. Research on mixed protein systems mainly focuses on improving the physical-chemical properties of mixed proteins and exploring the effects of different treatments on the interaction between mixed proteins. However, research on the functional properties of the SPI-WPI mixed protein system by ultrasonic has not been reported. We mainly explored the effects of the emulsification and gel property after the ultrasonic treatment (450 W, 30 min) of different mass ratios (1:9, 3:7, 5:5, 7:3, 9:1). The different mass ratios of without ultrasonic SPI-WPI mixed protein were designed as a control to explore the mechanism of ultrasonic treatment on the functional properties of mixed proteins. Our studies showed that the complementary effects of mixed proteins were mainly reflected in the interaction between soy protein isolate and casein or whey protein in milk forms a "key cluster" to promote efficient use of amino acids. This essay study aimed to prepare a high-emulsification and gelatinous mixed protein food to provide a theoretical basis for the development of new biprotein foods.