Abstract: Gas chromatographic method was used for the determination of p-methyl benzenesulfonyl isocyanate (MBSIC),the content was calculated by the method of normalized peak area.Experimental results showed that MBSIC was stable in atmosphere of oxygen and under high temperature,but unstable to light irradiation and moisture.Sample of MBSIC should be stored in dry and closed container filled with nitrogen and placed in dark place.