Abstract: In this study, the physicochemical and functional properties of Idesia polycarpa whole fruit protein (IPWP), Idesia polycarpa pericarp protein (IPPP), and Idesia polycarpa seed protein (IPSP) were compared. To reveal the differences in the properties of Idesia polycarpa proteins in different extraction sites, it was also compared with commercially available soybean protein isolate (SPI) to explore the potential of Idesia polycarpa protein application. It was found that the protein content (69.13%±0.61%) and total amino acid content of IPSP were significantly higher than those of IPWP and IPPP (P<0.05). The three Idesia polycarpa proteins all exhibited a porous structure, with molecular weights below 45 kDa, among which IPSP had the most extended structure and the highest content of the 18.4 kDa subunit. At the same pH, IPWP and IPSP showed smaller average particle size and higher absolute value of Zeta-potential and surface hydrophobicity than IPPP. The three Idesia polycarpa proteins demonstrated superior solubility, foaming capacity, and emulsifying activity compared to SPI. Compared with IPWP and IPPP, IPSP possessed enhanced solubility, foam stability, emulsification and emulsion stability, especially at pH 7, the solubility and emulsion stability of IPSP increased by 79.48% and 43.65%, respectively, than those of IPPP. In summary, the performance of the three Idesia polycarpa proteins was better than that of the commercially available SPI. IPSP showed the greater advantages in protein composition and functional properties. This study would provide the basic theoretical and technical support for the high-value utilization and development of Idesia polycarpa functional components.