This study investigated the formation mechanisms and gelation properties of soybean hull polysaccharides (SHPs)-soybean protein isolate (SPI) composite gels under varying SHP concentrations (0–2 %, w/v) and pH conditions (2.0–11.0). Key parameters analyzed included conformational changes, intermolecular forces, microstructure, water holding capacity (WHC), texture, and moisture migration. The results demonstrated that hydrophobic interactions, disulfide bonds, and hydrogen bonds were the primary forces stabilizing SHPs-SPI gels, while ionic bonds contributed the least, regardless of SHPs concentration and pHs. The addition of SHPs led to a decrease in surface hydrophobicity and intrinsic fluorescence, whereas WHC, texture properties, and zeta potential increased correspondingly. Electrophoresis revealed the formation of macromolecular aggregates with molecular weights exceeding 245 kDa upon SHPs addition. At pH 2.0, gels exhibited a positive surface charge with the lowest zeta potential (1.08 ± 0.12 mV) and the most dispersed water distribution. However, negative zeta potential was found at pH 7.0 and pH 11.0. Gels at pH 7.0 exhibited the lowest WHC (69.66 % ± 2.53 %) and hardness (114.79 ± 3.72 g), while pH 11.0 resulted in the lowest surface hydrophobicity (100.8 ± 9.21). These findings provide valuable insights into the pH and polysaccharide concentration-dependent mechanisms governing the formation of SHPs-SPI composite gels, supporting the potential application of SHPs as functional gelling agents in food systems.