Abstract: To study the auto-thermal reforming process of methane-wet air in a micro-combustor, a straight tube experimental system has been established with a tube diameter of 2 mm, based on which experimental tests and 3D numerical simulation are performed to analyze the conversion characteristics of the reforming, focusing on the influence of reaction temperature and feed gas ratio on the methane conversion rate and H₂ yield. Study results show that at the same mass flow of methane, both the methane conversion rate and H₂ yield increase with rising temperature, air-methane ratio and steam-methane ratio; the influence of air-methane ratio on methane conversion rate is greater than on H₂ yield. The system with low mass flow of feed gas is more efficient than that with high mass flow in H₂ yield during methane-wet air reforming. Test results agree well with that of the numerical simulation.