Abstract: In this paper, the betanin was studied to improve the thermal stability of betanin. Starch-based microcapsules loaded with betanin were prepared by starch adsorption and polysaccharide encapsulation. Firstly, single factor experiment was used to screen starch categories, polysaccharide categories, addition of sodium alginate, addition of ascorbic acid and addition of betanin. Then, the microcapsules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR), and the stability mechanism was also further analyzed. Finally, the thermostable betanin microcapsules were applied to the hot-processed food to verify their application effect (the betanin-colored dough was steamed in boiling water for 12 min). Results showed that the optimum preparation technology and formula of starch-based microcapsules loaded with betanin were corn starch, the best adsorption time of betanin by starch was 2 h, the best mass ratio of corn starch to betanin was 30:3, the best ratio of corn starch (wet base) to sodium alginate was 3:0.03, the best ratio of corn starch to ascorbate was 60:1, and the best retention rate of betanin was 73.42% after steam heating for 12 min. In addition, the appearance of the betanin microcapsules was dark red with fine particles. SEM indicated that the betanin was adsorbed into the starch interior, and sodium alginate wrapped around the starch particles to form a physical protective layer. FTIR (765 cm⁻¹) also confirmed that the betanin had been successfully loaded into the microcapsules. Through application in thermally processed foods, the color difference value ΔE after heating was 12.11+0.83 (microcapsules)<22.01+2.82 (control group), indicating the highthermal stability of microcapsules. Therefore, the heat stability of betanin can be improved by using starch as adsorbing material, ascorbic acid as color fixative and sodium alginate as embedding agent, the results also provide some theoretical basis and reference for the application of betanin in food processing.