Abstract: Isolated spleen lyrnphocry tes of rat having been exposed to 10-1000μrn mustaid gas at 37℃ 30minutes DNA damage lymphocytes at 424 and 72h postexposureweremeasured with SCG assay T he results not only show ed that time-dependent relationship and dose dependent relationship between mustard gas and DNA m igration and the percentage of DNA-danaged lymphocytes but also a highly significant increase in DNA dan age at 10^-3M,10^-4M after 4h postexposure compared w ith the control group It's suggested that the method may be used as and indicator of crytotoxi;ity resulted fmmmustard gad and also it may play certain role in early diagnosis in mustard gas intoxication.