The invention discloses a preparation method of a rhizoma gastrodiae capsule, and particularly relates to a method that effective ingredients are extracted from rhizoma gastrodiae through an aqueous extraction mode. Due to the effective ingredients such as gastrodin and polysaccharide in the rhizoma gastrodiae have the high solubility in water, the effective ingredients of rhizoma gastrodiae can be sufficiently extracted, acrylic resin is added in the extraction process, the multi-hydroxyl structure of acrylic resin is combined with the effective ingredients of the rhizoma gastrodiae, the fatsolubility of the effective ingredient of the rhizoma gastrodiae is enhanced, absorption is improved, after the rhizoma gastrodiae extract is dried and smashed, a lactic acid ethanol solution with thecertain concentration is adopted to conduct pelletizing, the characteristics of lactic acid are utilized for being combined with acrylic resin to form a new polymer to wrap rhizoma gastrodiae dry plaster powder, the hygroscopicity of the rhizoma gastrodiae dry plaster powder is reduced, the product stability is improved, and the rhizoma gastrodiae capsule with the good stability, high dissolvingspeed and good absorption performance can be obtained, under a harsh condition, the dissolving speed of the rhizoma gastrodiae capsule cannot change obviously, and the stability is good.