The invention provides a refining method of normal-butyl isocyanate. The method comprises the following steps: providing normal-butyl isocyanate solution to be refined, adding alchlor and dropwise adding a sodium hydroxide solution to the normal-butyl isocyanate solution to be refined at minus 10 to minus 5 DEG C while stirring, ensuring that reaction is performed for 0.5 to 1 hour, so as to obtain mixed liquor, ensuring that the mixed liquor is subjected to standing and layering, and separating and purifying an organic layer in the upper layer, so as to obtain the normal-butyl isocyanate. According to the refining method for normal-butyl isocyanate, impurity acid and a poly (normal-butyl isocyanate) floccule in the normal-butyl isocyanate to be refined are neutralized by using by the sodium hydroxide under the action of alchlor, then standing and layering are carried out, and the organic phase in the upper layer is separated and purified to obtain the normal-butyl isocyanate; according to the method, the product quality is improved.