Abstract: To investigate the stability and functional properties of binary (SPI-SA, SPI-RRTP) and ternary (SPI-SA-RRTP) complexes of soy protein isolates (SPI) with sodium alginate (SA) and Rosa roxburghii tratt polyphenols (RRTP). SPI, SA and RRTP were used as raw materials to prepare the complex, and the preparation conditions were optimized by single factor and response surface experiments. The complexes were characterized by particle size, polymer dispersity index (PDI), Zeta potential, fluorescence spectrum, surface hydrophobicity, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The results showed that the SPI addition was 2.95%, SA addition was 0.036%, RRTP addition was 0.25%, pH was 7.57, and the particle size was 140.41 nm. The theoretical combination was experimentally verified. The SPI-SA-RRTP ternary complex has the smallest particle size (140.93±0.32 nm) and PDI (0.155±0.004), the largest Zeta potential (−31.06±2.20 mV) and the best stability. Compared with SPI and binary complexes, ternary complexes have significantly improved binding tightness, hydrophilicity, thermal stability and oxidation resistance. SPI-SA-RRTP nanocomposite can be widely used in food industry, and provide new ideas and directions for its application.