The invention provides a method for preparing high-purity nisin, which comprises the steps of taking coarse powder of nisin as a raw material, dissolving, stirring, then standing, carrying out centrifugal phase separation, removing impurities, sampling, dissolving, carrying out the centrifugal phase separation again, removing the impurities, sampling, and drying, thereby preparing a product with the purity of more than 98%. The method has safe and simple technological method and high product purity, thereby being a good nisin purifying technology and being extensively used in the large-scale industrial production process.