A pot experiment was carried out to explore the response ability and mechanism of flue-cured tobacco to UV-B radiant intensity using varety Hongda and K326 as material. The tobacco agronomic characteristics, the contents of photosynthetic pigment and polyphenols, the vigor of root system and the activities of the antioxidant enzymes were determined. The result showed that tobacco height, the contents of chlorophyll A, chlorophyll B, total chlorophyll, lutein, carotene, chlorogenic acid and rutin were improved. The activities of both POD and root dehydrogenase were more higher compared to the control group while CAT was lower comared to the control group. And the biggest increase of pigments is lutein, then carotene and chlorophyll B, and finally chlorophyll A. The increase of the content of rutin was larger compared to that in chlorogenic acid. The range of variation of antioxidant enzyme activity increased with radiant intensity increased. It suggested that flue-cured tobacco can adapt to UV-B radiation enhancement by adjusting the contents of light oxidation resistance substance and antioxidant enzymes activities. Furthermore, a large difference of the response ability to UV-B radiation existed between two flue-cured tobacco varieties. And that of Hongda was much stronger than that of K326.