The present numerical study investigates the effect of a bluff body on outer wall temperature of a micro scale combustor. Combustion of lean premixed hydrogen-air mixture is simulated in two dimensional domain utilizing detailed chemistry of Li et al. (13 species with 19 chemical reactions) and different mass diffusivity for each species. The effect of bluff body in combustor is studied in two viewpoints: shape of bluff body and number of bluff bodies. Two shapes of bluff body, square and triangular shapes, are considered to study the combustion efficiency and outer wall temperature. The results indicate that the shape of bluff body does not have important effect on outer wall temperature. However, triangular shape outer wall temperature is slightly more than square shape. Results also show that combustion efficiency of the square bluff body is larger than the triangular one. In second part, the effect of number of bluff bodies (i.e. one, two and four bluff bodies) on the micro scale combustor is examined on combustion characteristics. With increasing the number of bluff bodies, the outer wall temperature increases. This is due to the formation of a uniform temperature field in the micro scale combustor.