<p>Astaxanthin (AST), as a potent natural antioxidant, holds broad application prospects in the functional food sector. However, its poor water solubility, low chemical stability, and insufficient bioaccessibility severely limit its practical efficacy. To overcome this bottleneck, this study developed a novel AST microencapsulation delivery system based on thermally induced gelation of soy protein isolate (SPI) and chitosan (CTS), with structural solidification achieved through freeze-drying technology. Through systematic optimization of the AST-to-wall material ratio (1:2), the prepared microcapsules achieved a 92.63% encapsulation efficiency. Microscopy and spectroscopy approaches confirmed that the microcapsules exhibited a regular spherical structure, with AST uniformly dispersed in an amorphous state within the wall material matrix. In vitro simulated digestion experiments demonstrated that encapsulated AST exhibited a 1.67-fold increase in gastrointestinal retention and a 4.5-fold improvement in bioaccessibility compared to free AST. This enhancement was primarily attributed to the physical protection provided by the wall material and its sustained-release properties in digestive fluids. Long-term stability assessment (26 weeks) further validated the advantages of this delivery system. At 4&#xa0;°C and 25&#xa0;°C, AST retention in microcapsules increased by by 38% and 41%, respectively, with half-lives extended to 114 days and 78 days. The SPI/CTS gel template method proposed in this study offers a safe and efficient physical cross-linking strategy for stabilizing AST, achieving synergistic improvements in stability and bioaccessibility without chemical modification. This technological system holds significant application value in the development of nutritional supplements and functional foods, providing a reference model for the delivery of liposoluble active ingredients.</p> Graphic abstract <p></p>