Abstract: The greenhouse effect of methane is 25 times that of the same volume of carbon dioxide. The low-concentration methane (especially the ventilation air methane) emitted from coal mining is huge and discharged into the atmosphere, which wastes energy and intensifies the earth greenhouse effect. The catalytic co-combustion of the low-concentration methane in the mine exhaust air and the coal in the boiler under high efficiency catalyst can be achieved, which can not only realize the complete combustion of the low-concentration methane in the mine exhaust air, but also reduce the greenhouse effect caused by methane emission. Furthermore, it promotes the full combustion of coal in the boiler, which increases the heating value of coal-fired boiler. A Co₃O₄/SiO₂-x catalyst with con-trollable particle size of Co₃O₄ and supported on silicon dioxide was prepared by using piperazine and pyromellitic acid hydrate as linker at different calcination temperatures. A series of characterization methods such as XRD, BET, H₂-TPR and O₂-TPD were used to study the physical structure and chemical properties of the catalysts and establish the structure-activity relationship between the physical and chemical properties of the catalyst and the catalytic combustion performance of low-concentration methane. On this basis, the optimal catalyst was selected and its catalytic performance of low-concentration methane and lignite co-combustion was investigated to reveal the catalytic co-combustion mechanism of low-concentration methane and lignite. The results show that the Co₃O₄/SiO₂-500 has the best catalytic activity in the same series of catalysts due to its smallest Co₃O₄ particle size, rich Co³⁺ species content and excellent oxygen transfer ability. In the catalytic co-combustion system of low-concentration methane and lignite, the addition of the Co₃O₄/SiO₂-500 catalyst effectively promotes the rapid precipitation and combustion of lignite volatiles, and the heat released from combustion provides the necessary high temperature conditions for methane combustion, which reduces the complete combustion temperature of low-concentration methane from 900 ℃ to 700 ℃. This study lays a theoretical foundation for the efficient and large-scale utilization of low-concentration methane in the mine exhaust air, energy saving and emission reduction.