The invention discloses an aziridine compound cyclizing method adopting a ketoxime. According to the method, an aziridine compound activated with tosyl is adopted as an initial raw material, the ketoxime is adopted as a nucleophilic reagent, and the aziridine compound is subjected to cycloaddition in acetonitrile or chloroform under the catalytic functions of potassium hydroxide, potassium carbonate, potassium tert-butoxide or triethylamine. Reaction processes of the method are simple. The method adopts the potassium hydroxide or the triethylamine as a catalyst and is environmental friendly, mild in conditions and wide in universality. High yields and good regioselectivity can be achieved for aziridine compounds with different structures and ketoximes with different structures.