This paper presents a three-dimensional combustion model in the microcombustors. In this research, the flame structure is composed of three zones: a preheat zone, a reaction zone, and, finally, a post-flame zone. The governing equations are solved in these zones using the required boundary and matching conditions, which are achieved from nonasymptotic or asymptotic approach. Moreover, the role of Peclet number as a determining factor in the microcombustor performance is analyzed, and is found that by the increase of the Peclet number, the dimensionless flame temperature rises. Consequently, this three-dimensional model has provided a great description for the Peclet number, the dimensions, the asymptotic or nonasymptotic assumption effects, and the structural heat conduction in the microcombustors. The results are validated with those obtained from two-dimensional heat transfers modeling, and are in accordance with data published by former researchers.