Self-assembled protein nanofibrils have attracted much attention due to their unique functional and biological characteristics. In this paper， cold-set gel was formed by adding CaCl2 and NaCl to soy protein isolate（SPI） fibrillated solution. The effect of various protein concentrations and ion concentrations on the properties of cold gels were investigated. Rheological measurements and the fitting results of Percolation model indicated that the critical percolation concentration（cp） of cold gelation was much lower than that of heat-induced fibril gelation. The lowest value of cp was obtained when the concentration of CaCl2 and NaCl was 30 mmol/L and 150 mmol/L， respectively. These gels showed isotropic force percolation and a homogeneous network. The increasing SPI concentration resulted in an increase of storage modulus （G′）， hardness and water-holding capacity（WHC）， as well， required a lower ion concentration to induce the gelation. At low ionic strength （CaCl2<50 mmol/L， NaCl<150 mmol/L）， the greater the ionic strength， the greater G′， hardness and WHC. With increasing salt concentration， G′， hardness and WHC presented decreasing trend. At the same ionic strength， cp of NaCl induced gels was higher than that of CaCl2 induced gels， which illustrated that salt bridges formation was the driving force to form cold gel rather.