The invention relates to a self-assembly body formed by starch and allicin in garlic and an application of the self-assembly body as a plant bacteriostatic agent and belongs to the field of food additives. Iodine binding experiments prove formation of the self-assembly body formed by starch and allicin in garlic, thermal stability analysis of the starch-allicin self-assembly body proves that formation of the self-assembly body can well improve the thermal stability analysis of the allicin in the garlic. Bacteriostatic experiments find that the self-assembly body has a good bacteriostatic effect on escherichia coli, staphylococcus aureus, bacillus subtilis and salmonella. The self-assembly body can serve as the plant bacteriostatic agent to be used for preparation of a bacteriostatic agentand a preservative; and besides, the self-assembly body can serve as the bacteriostatic agent to be used for a feed additive. A product of the starch-allicin self-assembly body has good thermal stability and bioactivity, a preparation process is simple, the cost is low, sources are wide, no chemical reagents are added, materials are common natural materials, and the self-assembly body has no toxicor side effects and has good application prospects.