Abstract:[Objective] Increases in atmospheric CO2 concentration have certain direct or indirect impacts on CH4 emission from rice paddy fields. So it is of great significance to have an in-depth study on impacts of long-term elevated atmospheric CO2 concentration on CH4 emission and related microorganisms for assessing and managing CH4 emissions from rice paddy fields in the context of future climate.[Method] To investigate effects of long-term elevated atmospheric CO2 concentration on CH4 emission and its mechanism, CH4 emission fluxes and abundance of the methanogens and methanotrophs under ambient CO2 (ACO2) and elevated CO2 conditions (ECO2) in rice paddy fields were monitored during the 2016-2017 season, with the aid of the Chinese rice FACE platform that has been operating for more than 10 years. Moreover, meta-analysis was conducted to determine quantitatively effects of elevated CO2 relative to duration on CH4 emission from and the abundances of methanogens and methanotrophs in rice paddy fields.[Result] Results show that compared with ACO2, long-term ECO2 significantly reduced CH4 emission and the abundance of methanogens by 28% and 39%, respectively (P<0.05), but increased the abundance of methanotrophs by 21% (P>0.05). Meta-analysis shows that with the increase in duration of CO2 elevation, the effect of elevated atmospheric CO2 concentration promoting CH4 emission and the abundance of methanogens gradually decreased, while the effect on the abundance of methanotrophs gradually increased.[Conclusion] Therefore, it could be concluded that under future climate conditions, long-term elevated CO2 will reduce CH4 emission from rice fields, which is of great significance for mitigating the greenhouse effect brought about by rice cultivation.