Plant　protein-based　nano-delivery　systems　have　rencently　drawn　increasing　attention,　and　several　physical　and　chemical　methods　for　improving　the　functional　properties　of　plant　proteins　have　been　reported.　In　this　work,　we　applied　ultrasonication　and　pH-shifting　combined　treatment　on　soy　protein　isolates　(SPI)　and　investigated　the　structure　changes　of　SPI　and　its　effects　on　the　formation　of　SPI-　sodium　alginate　(Alg)　electrostatic　complex　and　SPI-resveratrol　nanocomplex.　It　was　found　that　the　combined　ultrasonication/pH-shifting　treatment　resulted　in　a　smaller　particle　size　and　larger　surface　hydrophobicity,　which　were　114.6　±　1.2　nm　and　12741　±　456,　respectively.　During　the　formation　of　the　complex　with　Alg,　compared　with　pH-shifting　or　ultrasonication　treatment,　the　combined　ultrasonication/pH-shifting　treatment　expanded　stable　region,　where　the　particle　size　was　smaller　and　the　binding　constant　with　sodium　alginate　was　higher.　Moreover,　the　encapsulation　efficiency　of　resveratrol　in　SPI　increased　to　91.4　±　4.3%　after　the　combined　ultrasonication/pH-shifting　treatment.　Thus,　simultaneous　treatment　combining　ultrasonication　and　pH-shifting　was　significantly　more　effective　than　ultrasonication　alone　and　was　thought　as　an　effective　method　for　protein　modification.　©　2020　Elsevier　Ltd