The invention discloses a sodium perborate preparation method, which comprises: adding borax into a sodium hydroxide solution with a mass fraction of 30-35%, and stirring to prepare sodium metaborate,wherein 120-130% of the required amount of the borax is prepared; slowly adding 3-5% of a hydrogen peroxide aqueous solution into the prepared sodium metaborate solution, carrying out a reaction for30-50 min by controlling the reaction temperature at lower than 10 DEG C, adding sodium chloride to the reactor after completing the reaction, continuously reducing the temperature of the reactor to below 0 DEG C, precipitating the generated sodium perborate, and carrying out centrifugal dehydration in a centrifuge; and drying at a low temperature to obtain the finished product. According to the present invention, the preparation method has advantages of simpleness, low production cost and extremely high economic benefit.