The invention discloses a method for preparing high-purity bulleyaconitine A. The method comprises the following steps of: soaking a fresh radix aconiti agrestis root in acid aqueous solution, performing homogenate extraction and cavitation mixing solid-liquid extraction, collecting and concentrating the filtrate, and respectively performing gradient elution to obtain a crude bulleyaconitine A product through ion exchange resin column chromatography and macroporous adsorption resin column chromatography; and uniformly mixing crude bulleyaconitine A product and ethanol aqueous solution, dissolving in a water bath, cooling the filtrate to room temperature, standing and crystallizing at the temperature of 4 DEG C, repeatedly washing the crystal by using the ethanol aqueous solution, and obtaining a final product. According to the method, crushing and extracting are finished in one step through a homogenization method, and the method has the advantages of zero dust and simple flow. By adoption of a negative-pressure cavitation extraction technology, the mass transfer rate is improved, heating is not required, and the production period is shortened; and moreover, the reagents used in the whole process are ethanol and water, the organic solvent amount is greatly reduced, the production cost can be reduced, the environmental pollution is reduced, and the method has good application prospect.