The polar components in hydro-treated lubricating base oil are discussed in this paper. Cation-exchange resins, anion-exchange resins, and silica gel are employed for the separation of polar components from oil, and the relevant characteristics method of element analysis, hydrocarbon constituent ana lysis, and infrared spectroscopy are used. The effects of these fractions on free radical reaction studied via styrene radical polymerization at the temperature of 60 degreesC indicated that,with increasing acidity, the fractions restrain the free radical reaction. Finally, regarded as a special additive, the polar component effects on free radical reaction are studied, and the related kinetic equation shows that the reaction rate is directly proportional to the concentration of polar components.