Abstract: Potato protein is recognized as a high-quality plant-derived protein due to its high digestibility, balanced amino acid composition, and particularly high lysine content. Compared with many other plant proteins, potato protein exhibits favorable functional properties, including excellent solubility, emulsification ability, and gelation capacity. Because of these characteristics, potato protein has attracted increasing attention in the food industry and has been widely applied in various processed foods, especially frozen and refrigerated products. In such systems, protein gels often serve as structural matrices that determine texture, water retention, and product stability. However, during freezing, the formation and growth of ice crystals within the gel matrix may disrupt the protein network, resulting in structural damage, moisture migration, and deterioration of textural quality. Therefore, improving the freeze resistance of potato protein gels is essential for expanding their application in frozen food systems. In the present study, potato protein was modified using two physical–chemical strategies: pH-shift treatment and ultrasonic treatment, as well as their combined application. These modification methods have been widely reported to alter protein conformation, promote molecular unfolding, and enhance intermolecular interactions, thereby influencing gel formation behavior. The textural properties, color difference, gel-participating protein content, and microstructural characteristics of the resulting potato protein gels were systematically analyzed both before and after freezing. The primary objective of this work was to establish a relationship between the structural characteristics of modified potato proteins and the gel properties formed during freezing. In addition, the study aimed to clarify the effects of pH-shift and ultrasonic modification on the freezing behavior and stability of potato protein gels, thereby providing insight into the mechanisms through which protein molecular structure and gelation patterns regulate freeze resistance. The results showed that untreated potato protein gel exhibited a gelation temperature of 86.00℃, a gel hardness of 0.327 N, and minimal cohesiveness. The resulting gel presented the roughest surface morphology, with visible granular aggregates and relatively uniform pore size distribution. Following ultrasonic treatment, the gelation temperature remained unchanged at 79.86℃, while gel hardness increased to 0.356 N, producing a slightly smoother gel structure with a more uniform pore size distribution. Gels prepared using pH-shift treatment exhibited a finer microstructure and lower phase-change enthalpy, with 84.14% of the proteins participating in gel formation. The gel modified by the combined pH-shift and ultrasonic treatment exhibited the most refined structure, characterized by a smooth surface, uniformly small pores, and the lowest phase-change enthalpy and temperature. In addition, the soluble protein content decreased to 16.39%. After freezing, the water-holding capacity of untreated potato protein gel decreased to 76.8%. Ultrasonically treated gels showed a reduction in water-holding capacity to 79.16%. In contrast, pH-shift-treated gels exhibited only slight and uniform changes in pore size, with water-holding capacity maintained at 82.43%. The gel modified by the combined pH-shift and ultrasonic treatment showed the smallest variation in pore size and the minimal decrease in water-holding capacity. In this system, the soluble protein content decreased by only 16.39%, the freezing enthalpy of water in the gel was −238.54 J/g, and the average pore size was approximately 3 μm. Overall, the results demonstrate that potato protein modified by the combined pH-shift and ultrasonic treatment forms a fine and intact gel network structure, which effectively restricts water migration and ice crystal formation during freezing, thereby enhancing freeze resistance. This combined modification strategy significantly improves the freezing stability of potato protein gels and provides a theoretical basis for the development of novel potato-based frozen products.