To study the effects of sweet potato protein hydrolysates (SPPHs) on the gel structural properties of sodium alginate (SA) and to achieve the high quality utilization of sweet potato processing residues, SPPHs with different molecular weights (1000,2000,3000,8000Da) were added to SA to investigate their effects on the formation process and gel properties of SA gels induced by calcium ions in terms of gelation process, critical gel behavior, textural properties, water distribution and microstructure. The results showed that the interaction between SPPHs and SA promoted its cross-linking with calcium ions, which could strengthen the intermolecular structure, accelerate the appearance of critical gel point in the process of calcium cross-linking and reduce the amount of calcium ions required for the critical point. Among them, SPPHs with molecular weight of 8000Da had a more significant strengthening effect on SA gel, and the reaction sensitivity with calcium ions was the strongest, resulting in the formation of the largest gel strength. The average value of the storage modulus G′ value of SA-SPPHs8000 during the gelation process with 0.100% CaCl₂ was 17.05kPa. It was much higher than that of blank group SA (2.14kPa). The composite gel with the addition of SPPHs behaved as a typical non-Newtonian fluid, and the larger the molecular weight of the added SPPHs, the stronger the internal structural cross-linking of the formed composite gel, the stronger the pseudo plasticity, and the greater the viscosity. In addition, the addition of SPPHs significantly improved the hardness, elasticity and chewiness of SA gel beads, and improved the water holding capacity and internal structural stability of the gel beads. The results showed that the addition of SPPHs could strengthen the internal structure of SA gels and promote calcium cross-linking to form more compact three-dimensional network gels, which in turn improved the texture and other properties of SA gels. Compared with other protein hydrolysates, SPPHs had greater advantages. Meanwhile, this study could broaden the application scope of sweet potato protein, improve its added value and further realize the comprehensive utilization of sweet patato protein resources.