Abstract: The effects of solid concentration on molecular weight distribution, nitrogen solubility index, dispersion stability, water holding capacity, emulsifying property, foaming property and foam stability of soybean protein isolate were studied systematically in this paper. The results showed that the PR23-modifed soy protein isolate resulted in a higher NSI, foaming ability and dispersion stability, while lower water holding capacity, emulsifying activity and foam stability. High solid concentrations resulted in higher the dispersion stability, water holding capacity and emulsifying activity, while lower nitrogen solubility index and peptides concentration with molecular mass less than 10 kDa. When the degree of hydrolysis was less than 8%, the foaming ability of enzymatic hydrolysate of low concentration was higher than that of high concentration, while when the degree of hydrolysis was more than 8%, the foaming ability of enzymatic hydrolysate of high concentration was higher than that of low concentration.