Preparation method for pazufloxacin impurity compound

A provided preparation method for a pazufloxacin impurity compound comprises weighing (S)-(-)-10--(1-aminocyclopropyl)-9-fluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid, KO2 and a solvent, adding (S)-(-)-10--(1-aminocyclopropyl)-9-fluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid and KO2 into the solvent, reacting at 30-35 DEG C for 10-20 h, after the reaction is finished, washing with water, extracting, and concentrating, so as to obtain the pazufloxacin impurity compound 1. The compound is applied to pathology toxicology research of pazufloxacin medicine side effect. The preparation technology for pazufloxacin impurity compound is simple and high in yield.