NOVELTY - An oteracil potassium preparing method involves dissolving potassium hydroxide into water, cooling and adding potassium iodide to the obtained product. Allantoin is added to the obtained product. The obtained product is stirred and dropped bromine to the stirred product. Water is added to the filtered product, stirred and washed. The filtered product is dried to obtain the crude product. The oteracil potassium crude product is added into de-ionized water and slowly added potassium hydroxide aqueous solution to the product. The mixed product is washed and dried to obtain the refined product.    USE - Method for preparing oteracil potassium that is utilized for medicinal preparation.    ADVANTAGE - The method enables reducing reaction steps, eliminating the need of oxidant polluting environmental, simplifying refining process, reducing use of the organic solvent harmful for human body, saving preparing cost and increasing yielding rate above 65 percent. The oteracil potassium is suitable for industrial production. The product purity is reached more than 99.8 percent. The single impurity content is less than 0.1 percent.    DETAILED DESCRIPTION - An oteracil potassium preparing method involves dissolving potassium hydroxide into water and cooling to 0-10 degrees C. A potassium iodide is added to the obtained product and cooled to 0-5 degrees C. Allantoin is added to the obtained product. The obtained product is stirred and slowly dropped bromine to the stirred product. The obtained mixture is made to react at a temperature ranging from 1-5 degrees C. The reacted mixture is heated to 20 degrees C for 30-40 hours until the reaction is completed. A pH of the heated mixture is adjusted to 6 plus/minus 0.2 with acid and cooled to 0-5 degrees C. The obtained mixture is stirred and crystallized. The crystallized mixture is extracted and filtered. Water is added to the filtered product, stirred and washed for extraction and filtration. The filtered product is dried to obtain the crude product. The oteracil potassium crude product is added into de-ionized water and slowly added potassium hydroxide aqueous solution to the obtained product. The obtained product is stirred until the mixture is clear. The un-dissolved substance is filtered away. An acid is dropped into the filtering liquid to adjust pH to 6 plus/minus 0.2 while stirring. The obtained product is crystallized and filtered. Water is added to the filtered product and mixed. The mixed product is washed and dried to obtain the refined product.