In this paper, polar components in the UV-irradiated hydrotreated naphthenic rubber base oil were analyzed in detail. First, polar components were isolated from the base oil by silica gel column chromatography, and then they were characterized by a series of instrumental techniques, including elemental analysis, infrared spectroscopy, APCI/MS, and XPS. The results of the tests indicate that polar components comprise some aromatic heteroatom compounds of oxygen, sulfur, and nitrogen. Oxygen-containing compounds such as hydroxyl, carbonyl, and carboxyl groups constitute the main body of polar components. Nitrogen-containing compounds (NH2, NH, or NO2 and -N=N-) and sulfur-containing compounds (SO42- and sulfoxides) only account for minor percent of polar components. The molecular weight distribution of polar components is mainly concentrated between 200 and 500.