The combustion process, was numerical simulated based on the H2/O2 nineteen steps chemistry kinetics mechanisms and catalytic combustion mechanisms in a sub-millimeter parallel plate combustor, which is applied to a novel modular micro thermal photovoltaic system. The results show that the temperature of the combustor outside wall is affected by combustor height, H2/O2 ratio, nozzle shape. According to Optimization, A reasonable size and operating condition of the combustor for modular Micro-thermo photovoltaic system was obtained, the outside wall temperature increased 5.9%. Then the overall efficiency and power density of modular Micro-thermo photovoltaic system were calculated which is 18.69% and191.2mw/cm2respectively.