Abstract: Soybean protein isolate (SPI) was prepared from low-heat defatted soy flour, and preheated during alkaline extraction. The effects of alkaline-heating treatment (25, 50, 60, 70 and 80℃) on the solubility, thermal aggregation and rheological property of SPI were studied. The results showed that alkaline-heating treatment destroyed the protein solubility. The soluble portion of SPI samples contained a large number of aggregates which were mainly cross-linked by disulfide bonds. The alkaline-heating treatment could significantly improve the elastic modulus but decrease the gel point temperature of SPI samples. Alkaline-heating at 60℃ was proved to maintain a relatively fine solubility and exhibit the best elasticity of SPI.