【Objective】CH₄ is the second most potent greenhouse gas only next to CO₂. Continued CH₄ and CO₂ emissions by human activities pose a major challenge to the mitigation of global climate change. Rice paddy, a main form of artificial wetland, accounts for～8% of anthropogenic sources of CH₄. The elevated atmospheric CO₂(eCO₂) affect the cycling of nutrients and elements in paddy fields mainly through the changes in plant-soil-microbe interactions, which also influence net CH₄ flux associated with both the methanogenic and methanotrophic processes. However, how eCO₂ affects aerobic methane oxidation in paddy soils has rarely been examined, and the adaptative mechanisms of active methane-oxidizing bacteria(MOB)for eCO₂ remain unclear. This study aimed to explore the changes in methane-oxidizing rates and identify the active MOB phylotypes in paddy soil under the eCO₂ treatment.【Method】We collected paddy soil samples from China’s FACE(Free Air CO₂ Enrichment)experiment station, with FACE treatment and ambient CO₂ concentration treatment (aCO₂). The CH₄-feeding microcosm incubation was applied to learn the methane-oxidizing rates in the two soils. DNA-based stable isotope probing (DNA-SIP) combined with quantitative polymerase chain reaction (qPCR) of methane-oxidizing functional gene pmoA was used to identify the ¹³C-labeled DNA. High-throughput sequencing and phylogenetic analysis for the 16S rRNA gene amplicons of the ¹³C-DNA were used to identify the active microbiomes during methane oxidation.【Result】The results showed that eCO₂ significantly stimulated aerobic methane-oxidizing rate when compared to the ambient CO₂ treatment, with 302 and 243 nmol CH₄·g^–1 d.w.s·h^–1, respectively. The abundance of MOB increased by 1.1 folds -1.2 folds under eCO₂. A group of MOB assimilated ¹³CH₄ and synthesized ¹³C-DNA, which were separated into heavy fractions during DNA-SIP. The result of high-throughput sequencing for ¹³C-DNA showed that Methylobacter and Methylosarcina predominated the active MOB phylotypes. The relative abundance of Methylobacter increased by 16.2%-17.0% while the relative abundance of Methylosarcina decreased under eCO₂. eCO₂ also stimulated the activity of non-methanotrophic bacteria, such as Acidovorax and Pseudomonas, which implies a methanotrophy-induced microbial community response to eCO₂.【Conclusion】This study reveals positive effects of elevated atmospheric CO₂ on aerobic methane oxidation in paddy soil, with the predominant and active MOB of Methylobacter playing crucial roles, indicating an improved potential of methane oxidation under the scenarios of global climate change.