Abstract: To better use low grade tobacco,it was irradiated by UV,the UV treated samples were extracted with simultaneous distillation extraction,the aroma substances in UV treated tobacco were detected by GC/MS. The total sugar,total nitrogen and nicotine were determined.The results showed that the contents of alcohols, esters and lactones increased,while the contents of phenolic substances decreased significantly after UV irradiation.The contents of aldehydes,furans,nitrogen-containing heterocycles and cembranols reached their highest values by UV irradiation in 60 minutes.