High speed combustion characteristics of premixed stoichiometric air-acetylene mixtures inside microchannels are numerically studied by solving a Navier-Stokes (NS) system of equations with a single-step chemistry model. A two dimensional explicit finite volume solver has been developed using modified advection upwind splitting methods (AUSM+) to predict the complex interactions among hydrodynamic processes, shock structures and combustion in microdimensions. The effects of channel aspect ratio and wall temperature on high speed micro-combustion have been studied in this work. The increase in wall temperature due to wall friction in reduced dimensions initiates the chemical reaction of the combustible mixture near the wall region, and the reacted zone reaches the centerline for smaller height-to-length ratios of the microchannels. The wall temperature plays an important role in hypersonic combustion at the microscale.