The present invention belongs to the field of medicine and relates to a method for preparing an extract of Strychnos nux-vomica, the method comprising : (1) soaking Strychnos nux-vomica with a first alkaline solution, followed by performing solid-liquid separation to obtain a solid matter; (2) extracting the solid matter obtained in step (1) with ethyl acetate, followed by performing solid-liquid separation to obtain an extraction solution (3) subjecting the extraction solution obtained in step (2) to silica gel column chromatography to obtain an eluate, the eluent being an absolute ethanol or an ethanol solution added with at least one of an ammonia solution, a potassium carbonate solution, a sodium carbonate solution, a sodium bicarbonate solution and potassium bicarbonate solution; (4) drying the eluate to obtain a dried matter; (5) dissolving the dried matter in an acid solution, followed by performing solid-liquid separation to obtain a liquid matter; (6) adjusting the pH value of the liquid matter obtained in step (5) to 8-13, followed by performing solid-liquid separation to obtain a solid matter; and (7) subjecting the solid matter obtained in step (6) to recrystallization. The present invention relates to the extract of Strychnos nux-vomica and a medical use thereof. The extract of Strychnos nux-vomica of the present invention has a high content of brucine and a low content of strychnine, and is safe and effective for use.