The destruction of ozonosphere and the global warming have been widely concerned by governments and peoples all over the world. Increase of UV-B (ultraviolet-B) radiation on Earth's surface due to ozone layer depletion can decrease the growth and alter the chemical composition of litter fall of plant, and consequently change the microbial community composition, structure and activity in soil. Methane is an important greenhouse gas and has a global warming potential of 25 compared to CO_2 over a 100-year period. Its rank is second only to CO_2 in the atmosphere and its concentration in the Earth' s atmosphere in 2010 was 1.808 * 10~(-6) muL /L, up from 0.7 * 10~(-6) muL /L in 1750. In addition to abiogenic production of methane, there are biogenic methane as well. Biogenic methane produced by the process of methanogenesis usually occurred under highly anaerobic conditions, for example, in the guts of humans and other animals, especially ruminants, and in landfill, artificial and natural wetlands, etc. As a kind of wetland, flooded paddy can generate a lot of methane during plant growth and are considered to be one of the major anthropogenic sources of methane, especially the year-round flooded paddy field. Up to now, quite a few researches demonstrated that methane can be largely produced from plant tissues under the influence of UV (ultraviolet) radiation due to the generation of ROS (reactive oxygen species). ROS was suggested to be a potential free-radical mechanism which can produce CH_4 from plant polysaccharides under aerobic condition. Though the significant effects of UV-B radiation on methane emission from rice paddy field have been studied, the effects of UV-B radiation on the methane emission from year-round flooded paddy field are rarely studied. In this paper, Yuanyang Hani Terraces which is a typical year-round flooded paddy field in Yunnan, Southwestern China, was chosen to investigate the dynamics of methane emission under enhanced UV-B radiation. Field experiment was conducted to investigate methane emission as affected by enhanced UV-B radiation (7.5 kJ m~(-2) d~(-1)) in Yuanyang Hani Terraces where planted the rice traditional cultivar named Baijiaolaojing at the altitude of 1600 m. The CH_4 emission flux was measured by static chambergas chromatograph method with an interval of 10 days during the rice growing season. The results showed that: (1) The straw weight and root weight decreased significantly under enhanced UV-B radiation at different stages including late tillering stage, jointing to booting stage, heading to flowering stage and mature stage (P<0.05). (2) The seasonal and daily patterns of CH_4 emission were changed by the enhanced UV-B radiation. Only one emission peak during the whole growing season was observed at jointing to booting stage under the control, while two peaks were observed under enhanced UV-B radiation at jointing to booting stage and mature stage, respectively. Of the daily CH_4 emission, the second emission peak under enhanced UV-B radiation appeared in advance, compared with the control at mature stage. (3) There was a significant positive correlation between CH_4 seasonal emission flux and the temperature in chamber as a result of enhanced UV-B radiation (R = 0.789, P< 0.05). (4) The total amount of CH_4 emission were increased by 47.2%, 293.8% and 74. 4% significantly as compared with that of control at late tillering stage, jointing to booting stage and mature stage, respectively (P<0.01). The results suggest that enhanced UV-B radiation can stimulate CH_4 emission from rice paddy field cultivated with traditional rice cultivar.