Abstract: In this study,the thermal stability and secondary structures of soy protein isolate(SPI) during heat treatments were analyzed by differential scanning calorimetry( DSC) and fourier transform infrared( FTIR)spectroscopic. The impact of differences in sample concentration on denaturation temperature( T_D) and denaturation enthalpy(ΔH) were not obvious. The denaturation temperatures of 7S and 11 S in isolated soy protein without heat treatment were 74.2 ℃ and 93.7 ℃. Compared with untreated samples,the heat treatment resulted in an addition of α-helix structureand reduction of β-sheet structure. Heat treatment at 80 ℃,α-helix structure and β- turn structure showed a trend of increased firstly and then decreased. At 2 % protein concentration,90 ℃ heat treatment conditions,with the processing time of growth,α-helix structure and β-sheet structure showed a trend of first increase and then decrease,and random coil structure showed the opposite trend. In any protein concentrations conditions,90 ℃,heat treatment 45 min,11 S globulin degeneration,increased the content of random coil structure,while reduced the component content of β-corner structure andβ-sheet structure.