Abstract: A new kind of nitrone, 2, 4,-dinitrophenyl-t-butyl nitrone (DNPBN), has been used for investigating the photolytic mechanism of chlorohydroearbon and trapping active chlorine atom and other C-centre radicals produced therein. The results show that under the irradiation of high-pressure mercury lamp, for polychlorohydrocarbon, the more the substitute chlorine atom, the easier the homolysis of C—Cl bond of its and seldem chlorine can be trapped from mono- or dichlorohydrocarbons. On the other hand, both chlorine, a more persistent adduct (Cl—DNPBN)~· than other famillar adducts, such as (Cl—PBN)~·, can be obtained.