BACKGROUND: Gallic acid (GA) is recognized for its significant antioxidative and anti-inflammatory properties. The processing and consumption of GA-rich foods influence the interaction with cell wall polysaccharides, thereby impacting the bioavailability and bioaccessibility of GA. This study aimed to develop a biomimetic dietary fiber (BDF) model composed of bacterial cellulose, pectin, and GA to investigate the interactions, digestive behavior, and antioxidant synergism between polysaccharides and GA within the BDF. RESULTS: The microstructural, compositional, and crystalline characteristics of the synthesized BDF were found to be comparable to those of natural dietary fibers. During simulated digestion in the stomach and small intestine, a total of 38.02% of GA was released from the BDF, while 61.98% remained in a polysaccharide-GA conjugated form post-digestion. In free radical scavenging assays, the GA bound within the BDF exhibited a greater antioxidant capacity than free GA. CONCLUSION: The interactions between polysaccharides and GA are mediated by hydrogen bonding, hydrophobic interactions, van der Waals forces, and other non-covalent interactions. The release mechanism of GA involves its escape and diffusion from the BDF network structure, the disintegration of the BDF, and the dissolution of pectin. Polysaccharides provide a protective effect on the bioactivity of GA and enhance its synergistic role in antioxidative stress, thereby improving its bioaccessibility. These findings lay the groundwork for further exploration of the interaction mechanisms between polysaccharides and GA in dietary fibers and hold significant implications for the development of dietary intervention strategies aimed at mitigating oxidative damage. © 2025 Society of Chemical Industry.