The invention relates to a preparation method of high purity bulleyaconitine A. The preparation method comprises the following steps: root of radix aconiti feri of Yunnan is crushed, and acid alcoholic solvent or alcohol water solution is used for diacolation, and supersound or thermal refluxing extraction. The extracting solution is decompressed and concentrated to be non-alcoholic at the temperature of 80 to 90 DEG C, cooled down to room temperature, to ensure the relative density to be 1.00 to 1.30; standing is performed for 10 to 20 hours; the extracting solution is filtered; the pH is adjusted to 6.0 to 8.0 with basifier; and then the extracting solution is extracted with ethyl acetate or chloroform. The ethyl acetate or chloroform liquid is contracted, column chromatography is performed to the obtained paste, silica gel or neutral alumina are used as fillers, any one of solvent vapor-acetone-diethylamine, ligarine-acetone-diethylamine or cyclohexane-acetone-diethylamine is used for eluation, the bulleyaconitine A in the collected liquid is constantly checked during the thin layer chromatography, the collected liquid containing the bulleyaconitine A is merged, the solvent is concentrated, carbinol or ethanol is dissolved, filtering is performed, crystallization is performed at room temperature, filtering is performed, the crystal is repeatedly rinsed with carbinol or ethanol, and the final product is obtained. The purity of the obtained product is high, the production cost is low, and the toxicity of the used organic solvent is low.