This study introduces the theory of asphalt aging with infrared adsorption spectrum. Qualitative and quantificational comparisons are carried out between Karamay asphalt ultraviolet radiation aging, after which asphalt turns from sol-type to gel-type and other aging types. The variance ratio of absorbance A at 1700 cm-1 in infrared spectrum chart is consistent with the tendency of asphalt’s three general indexes, including penetration, ductility and softening point. The oxidation speed of ultraviolet radiation aging is 1.80~6.23 times that of thermal aging. In addition,the process of photo-oxidation, the order of carbonyl content in different asphalt samples, the influence of ultraviolet radiation on long term aging of asphalt and other useful information has been gained for better and further researches in this field.