Abstract: Proteins, polyphenols, and polysaccharides are components with distinct functional attributes. When proteins provide surface activity, polyphenols offer antioxidant activity, and polysaccharides contribute steric hindrance, the three can form ternary complexes through covalent bonds that are irreversible and highly stable. In most cases, the functional properties of these ternary covalent complexes are significantly enhanced compared to those of individual components or binary complexes. The nano-delivery systems formed by ternary covalent complexes protect the encapsulated bioactive substances from adverse factors in the gastrointestinal tract, such as oxidation, pH changes, and enzymatic degradation, thereby preventing their decomposition. This article provides an overview of the common preparation methods for binary and ternary covalent complexes of proteins, polyphenols, and polysaccharides, as well as the formation mechanisms of these complexes, their functional properties, and their applications in nano-emulsions, nanoparticles, and nano-gels as delivery systems. The review serves as a reference for designing ternary covalent complex systems aimed at encapsulating and protecting bioactive ingredients.