The invention belongs to the technical field of medicine, relates to preparation of an imatinib mesylate alpha crystal and a pharmaceutical composition thereof, and provides a preparation method of the imatinib mesylate alpha crystal. The method provided by the invention is short in reaction step, simple to operate, small in toxicity of a used solvent, small in environmental pollution, high in total yield, and low in cost. The prepared product is high in purity and applicable to large-scale industrial operation. The crystalline of the prepared imatinib mesylate alpha crystal is over 60%. The pharmaceutical composition containing the imatinib mesylate alpha crystal provided by the invention has the advantages that the defects of poor liquidity, unstable thermodynamics and strong hygroscopicity of the imatinib mesylate alpha crystal are overcome, and the prepared composition is even in content and strong in stability after long-term placement.
