This invention discloses an ionizing radiation protective adhesive and its preparation method. The ionizing radiation protective adhesive comprises the following components by mass percentage: 0.5%~1.5% guar gum powder, 0.25%~1% borax, 5%~10% humectant, 0.1%~0.5% preservative, 1%~20% bismuthoxide, 1%~20% lanthanumoxide, 0%~0.1% fragrance, and the balance being deionized water. This invention's ionizing radiation protective adhesive achieves seamless skin coverage, can be shaped arbitrarily, and greatly increases comfort. It is highly suitable for radiation shielding of local organs or tissues during radiological diagnosis and treatment, especially for local shielding in X-ray diagnosis of infants and young children, demonstrating strong practicality.