To investigate the differences in photosynthesis,protective ability and repair capability between the invasive weed Eupatorium adenophorum L.and the native weed Artemisia argyi Levl under the condition of enhanced UV-B radiation,we designed a seven-week experiment under the condition of UV-B radiation up to 0.46 mW·cm^-2·h^-1 and an extra experiment after stopping radiation to observe the changes in both species’ growth conditions.Moreover,the effects on photosynthetic capacity,the contents of oxides and antioxidants as well as the activity of antioxidant enzymes were measured and analyzed.And the results showed as follows:(1)the maximum photosynthetic assimilation rate (P_{n max}),photochemical efficiency in the light and maximal quantum yield of PSⅡ were restrained,but the former was showed more repressive significantly in E.adenophorum L.as the durations of UV-B radiation increased.(2)The contents of malonaldehyde (MDA) and super-oxygen ion (O^-·₂) in both species were accumulated as the durations of UV-B radiation increased,but the increased proportion of them was more significant in A.argyi Levl.(3)The contents of antioxidants concluding ascorbate (ASA) and glutathione (GSH) turned out different tendencies that the contents tended to firstly increased and then decreased in E.adenophorum L.while to increased and maintained a high level in A.argyi Levl.Besides,the enzymatic activities of peroxidase (POD) and superoxide dismutase (SOD) were improved remarkably after radiation in both species.And the enzymatic activity of ascorbate peroxidase (APX) in both species firstly increased and then decreased.As for the enzymatic activity of catalase (CAT),it was gradually inhibited in E.adenophorum L.but firstly enhanced and then inhibited in A.argyi Levl.As a consequence,we found the physiological mechanism of photosynthesis and antioxidation of E.adenophorum L.and A.argyi Levl responded to enhanced UV-B radiation were similar with some differences.