Flammulina velutipes polysaccharide (FVP) was added to soy protein isolate (SPI) hydrogels and subjected to heat treatment to improve the gel strength, water-holding capacity and thermal stability. The stability of FVP-SPI hydrogels was further analyzed in terms of their secondary and tertiary structures and intermolecular forces. The results showed that heat treatment and addition of FVPsignificantly improved the water-holding capacity of SPI hydrogels, and increased the enthalpy change of denaturation (ΔH) by 25.46%, thereby significantly improving hydrogel stability. Hydrophobic interactions, disulfide bonds and electrostatic interactions were the major driving forces for the formation of heat-induced FVP-SPI hydrogels. The addition of FVPimproved the electrostatic interactions and caused transformation of α-helix into β-sheets in the hydrogels, surface exposure of the tryptophan residues in SPI and enhanced hydrophobicity. The enhancement of SPI hydrogels by FVPprovides a reference for the development and application of SPI hydrogels.