The catalytic combustion characteristics of methane-air mixture inside the combustion chamber of a micro-engine were investigated experimentally and numerically. The catalytic combustion experiments of the micro-engine coated with the supported noble metal catalysts Pt-La/gamma-Al2O3 were investigated. Numerical simulations of methane-air combustion with detailed gas phase and surface catalytic reaction kinetics, heat transfer, and leakage were investigated to interpret the experimental results of micro-engine catalytic combustion. The experimental results indicate catalytic micro-combustion of methane-air mixture is possible in the spaces approximately the length of 0.34 mm and diameter of 3 mm. Catalytic micro-combustion of methane-air mixture is demonstrated at the equivalence ratios of 0.8 and 0.2. The free-piston position traces are identical during the compression stroke, but different during the expansion stroke. The mass loss causes product temperatures to decrease faster during the expansion stroke, and significantly decreases the cycle work of the micro-engine. Some theoretical evidences are provided for the application of catalytic combustion to a power micro-electromechanical system and the extension of the micro-combustion limits.