As China has gradually become the largest energy consumer and carbon emitter, the efficient utilization of CO_2 has become an important means in realizing the "dual carbon" strategy. Microbial catalytic reduction of CO_2 offers a low-cost solution for simultaneous green hydrogen storage and CO_2 conversion and utilization. This paper focuses on the establishment of CO_2 dry biomethanization method, and conducts experiments to identify the key factors affecting the conversion rate and microbial community structure. The results showed that maintaining a temperature of 35 ℃, employing an optimal H_2/CO_2 feed ratio of 4 ∶ 1, and implementing a 6-day soaking period for the nutrient solution in an anaerobic dry reactor filled with carbon sponge are critical for enhancing the conversion rate. Additionally, microbes at the end of the soaking cycle were sequenced and analyzed by high-throughput sequencing technology. The dry reactor exhibited dominance by anaerobic hydrogen-consuming methanogens, particularly at the genus level with Metanobacterium and Metaosaeta being prevalent. Moreover, the bacterial community displayed relatively high levels of Aconobacterium and Mesotoga. This study aims to investigate the key factors affecting the conversion rate of CO_2 dry anaerobic biomethanation and to analyze the structure of the microbial community, in order to provide a theoretical foundation and technical support for the process of microbial methane production.