Preparation method of imatinib mesylate beta-form crystal

The invention discloses a preparation method of an imatinib mesylate beta-form crystal. The method comprises the steps that imatinib alkali is suspended in organic solvent and cooled to 0-5 DEG C under the protection of nitrogen, a beta-form crystal is added, and methylsulfonic acid is dropwise added under the condition of heat preservation; after methylsulfonic acid is completely dropwise added, the temperature is raised to 20-30 DEG C, heat preservation crystallization is conducted for 2-6 h, and a white solid product is obtained after suction filtration and drying are conducted. According to the preparation method of the imatinib mesylate beta-form crystal, a one-pot method is adopted to direct prepare imatinib mesylate with the beta crystal form, other crystal forms or amorphous crystal transformation is not needed in the preparation process, the preparation technology is simple, the reaction conditions are mild, posttreatment is easy, the product purity is good, and the yield is high.