In　order　to　improve　the　gel　quality　of　soy　protein　isolate　(SPI),　a　new　two-step　gel-preparation　process　was　applied　in　this　study.　First,　SPI　dispersions　were　pre-aggregated　by　using　three　sulfates　(CaSO4,　MgSO4,　and　ZnSO4)　at　different　concentrations　(0~15　mmol/L)　and　then　gelled　by　adding　CaSO4　up　to　a　total　salt　concentration　of　35　mmol/L.　The　pre-aggregation　effects　of　different　salt　ions　on　the　structure　and　gelation　of　SPI　were　investigated.　The　results　showed　that　the　interaction　between　salt　ions　and　protein　molecules　was　a　spontaneous　endothermic　reaction　driven　by　entropy　change,　and　the　heat　change　caused　by　titration　of　ZnSO4　was　more　intense　than　that　of　CaSO4　and　MgSO4.　The　addition　of　salt　ions　caused　the　increase　in　the　content　of　α-helix,　but　decrease　of　β-sheet　structure　and　fluorescence　intensity.　At　the　same　addition　level,　the　particle　size　and　apparent　viscosity　of　SPI　aggregates　induced　by　ZnSO4　were　significantly　larger　than　those　induced　by　the　other　two　salt　ions　(P2+　had　stronger　aggregation　ability.　The　rheological　results　showed　that　compared　with　SPI　gel　without　pre-aggregation,　the　elastic　modulus　of　the　SPI　gel　prepared　by　pre-aggregation　with　10.0　mmol/L　CaSO4,　10.0　mmol/L　MgSO4　and　5.0　mmol/L　ZnSO4　were　increased　by　49.5%,　30.0%　and　59.9%,　respectively.　However,　excessive　aggregation　of　protein　molecules　led　to　the　decrease　in　gel　strength.　Therefore,　proper　pre-aggregation　of　proteins　with　different　salt　ions　could　effectively　improve　the　gel　properties.　These　results　might　provide　a　green　and　simple　method　for　the　texture　improvement　of　SPI　gel　products.　©　2022,　Editorial　Department　of　Journal　of　Food　Science　and　Technology.　All　right　reserved.