The invention relates to an alpha crystal form of 6-fluo-3-hydroxyl-2-pyrazinecarboxamide and a preparation method thereof. The alpha crystal form of 6-fluo-hydroxyl-2-pyrazinecarboxamide is white or off-white solid in appearance, has cell parameters as follows: alpha=90 degrees, beta=90 degrees and gamma=90 degrees, and has a spatial structure in lamellar arrangement, wherein molecules are connected through hydrogen bonds. The preparation method comprises the steps of: dissolving 6-fluo-3-hydroxyl-2-pyrazinecarboxamide in a solvent as per (1:5)-(1:20)g/ml, carrying out water-bath heating for dissolution, then, placing into a water bath at 25-40 DEG C, standing, and when crystals begin to separate out, carrying out crystallization at -15-0 DEG C; and filtering and drying in vacuum for 6-8h at 55-65 DEG C. The prepared alpha crystal form of 6-fluo-3-hydroxyl-2-pyrazinecarboxamide has high purity, high yield and stability; and the preparation method is simple in process and easy to implement and has the yield being 90-95% and the purity being not smaller than 99.90%.