Abstract: In order to further enhance the protective effect of protein-based microcapsules on Bifidobacterium bifidum in simulated gastric juice, alginate was selected as a double-coating material. It was observed that the optimal coating process condition was obtained by evaluating the particle size of microcapsules and survival rate of microencapsulated Bifidobacterium bifidum in simulated gastric juice, and that the optimal coating process condition was:the concentration of alginate solution 0.5%, the concentration of CaCl20.05mol/L, pH5.5, the agitation rate 500r/min. The particle size of microcapsules was 133μm, and the survival rate of Bifidobacterium bifidum in simulated gastric juice was improved to 14.5% at the optimal coating condition.