Abstract: Thermally irreversible polysaccharide gels do not convert from a solid or semi-solid state to a fluid state at high temperatures. They exhibit excellent flexibility, elasticity, and water retention capacity, along with superior thermal stability compared to thermally reversible gels. These properties make them highly promising for heat-resistant processed foods. Nowadays, there are four principal types of thermally irreversible gel products, namely sodium alginate, konjac gum, curdlan gum and gellan gum. This paper comprehensively reviews these four gels, focusing on their chemical structures, preparation processes, and functional properties, including gelling, stabilization, thickening, emulsification, biocompatibility, antimicrobial activity, and film-forming capability. Meanwhile, examples of applications of thermally irreversible polysaccharide gels in food fields, including rice and noodle products, fat substitutes, emulsion products and food packaging, and other fields are listed, aiming to provide a theoretical and practical basis for thermally irreversible polysaccharide gels in the field of food processing. Currently, the study of thermally irreversible polysaccharide gels is facing challenges such as unclear mechanisms, limited applications and insufficient structural optimisation. It is necessary to further clarify the irreversible mechanism, deeply analyze the intrinsic connection between colloidal structure and performance by employing physicochemical analytical techniques, and to develop a green preparation process. In addition, the thermal stability advantage of thermally irreversible polysaccharide gels should be fully explored to expand their potential applications in emerging fields such as high-temperature-resistant food processing and intelligent packaging.