The protein was pretreated with soy protein isolate (0, 6min 200W, 6min 400W, 6min 600W, 12min 600W and 24min 600W), then heated (100℃, 20min), centrifuged and dried to prepare soluble thermal aggregate. Aggregates, using ultrasoundfree pretreatment of soluble soy protein isolate (original soy protein isolate was dissolved in phosphate buffer and prepared by centrifugation) as a control, to investigate the structural characteristics (spatial structure, particle size distribution, functional group, potential, hydrophobicity) and emulsifying properties (emulsification and effect of emulsion stability). The results showed that compared with SSPI, USTSPI reached the maximum in the ultrasonic time and ultrasonic power of 6min, 600W, and the average particle size, absolute value of potential, protein dispersity index (PDI) and turbidity were decreased by 273.50nm, 6mV, 0.33 and 288.2, respectively. The carbonyl and disulfide bonds in the functional group were reduced by 0.26nmol/mg and 0.38μmol/g, respectively, and the free amino and free sulfhydryl groups were increased by 0.16μmol/mg and 0.59μmol/g. The βturn structure was increased, the β1 folded structure content was decreased by 11.97 percentage points; the surface hydrophobicity was increased by 36478, and the emulsification and emulsion stability were increased by 123.56m2/g and 360.95min, respectively. The above results indicated that the thermal aggregates can change the protein structure to reduce the emulsification properties of the protein, while the ultrasonic pretreatment can resist the degradation of protein emulsification activity caused by thermal effects to some extent, which provided a method for solving the problem of protein emulsification degradation caused by heating.