the invention relates to the technical field of medicines and chemical industry, and specifically relates to a refining method of oteracil potassium. the refining method comprises the steps of heating and dissolving oteracil potassium crude product in aqueous solution containing alkaline matter, filtering, adding one or more of polar organic solvent to filtrate, cooling and crystallizing, and filtering to obtain high-purity oteracil. by adopting the refining method, oteracil potassium with the purity more than 99.96% can be obtained and the yield achieves more than 90%. the refining method has the advantages of being easy and simple to operate, low in production cost and high product purity, and is suitable for industrial production and use.