The present disclosure relates to a novel crystalline form of lenvatinib mesylate and the preparation method thereof. The novel crystalline form of mesylate of the present disclosure can be used for treating invasive and differentiated thyroid cancer. The novel crystalline form of mesylate of the present disclosure has good solubility, stability, and remarkable purification effect in process. The preparation method of this novel crystalline form is simple, low cost, and has an important value for future optimization and development of the drug.