The present invention discloses a refining process for removing chlorate from perchlorate. According to the content of chlorate in the perchlorate the stoichiometric metasulfite solution or solid can be added, and reacted with chlorate to decompose the chlorate into the compound which can be easily dissolved in water. The perchlorate in the product does not produce reaction with said compound, and the small quantity of acid produced by reaction can be neutralized by alkali to make pH value of solution be 7-9, the content of chlorate in the perchlorate can be controlled in below 0.003% (by chloride) so as to reach to the index of high-quality product.