Excessive intake of saturated fatty acids poses a serious health risk, necessitating the urgent development of healthier plant-based fat replacers. Despite the emulsifying properties of chitosan (CS), it remains a significant challenge to create CS emulsions with minimal CS content and superior rheological properties as fat replacers. In this study, a supramolecular interaction system was constructed with inner hydrophilicity and outer hydrophobicity, enabling tunable rheological properties. This system was utilized to assemble hydrophobically modified CS with sodium alginate through appropriate treatment. As the oil phase fraction in the emulsion of stabilized flaxseed oil in the supramolecular system increases, the viscosity, storage modulus (G′), and loss modulus (G″) of the emulsion also increase. The emulsion transitions to a semi-solid state when the oil phase fraction ≥60 wt%. The supramolecular system (1 mg/g) can stabilize flaxseed oil emulsion with 80 wt% oil phase fraction. There were no significant changes in the morphology and rheological properties of the emulsions following a 60-day storage period at room temperature. In addition, emulsions can be used in several scenarios as fat replacers in food processing due to their tunable rheological properties. Display omitted •An inner hydrophilic and outer hydrophobic supramolecular system was constructed.•The supramolecular system (1 mg/g) can stabilize emulsion with 80% oil fraction.•Hydrophobicity of chitosan and rheological properties of emulsions are tunable.•Emulsions can be used in several scenarios as fat replacers in food processing.