Abstract: Methane and air premixed combustion around a cylinder is chosen to evaluate reduced mechanisms of 16species/41steps, 15species/19steps and 53spesies/325steps. The coming flows are homogeneous. Turbulence and its interaction with combustion, fuel diffusion are neglected and finite reaction rates of chemistry are assumed in the computation. The 5th order WENO scheme that conserves free flow properties is used to mitigate derivative errors from unsmooth grids and increase solution accuracy. Pressure and temperature contours as well as their distributions along stagnation line are obtained including mass fractions of species CH₄, CO and CO₂. Bow shock and flame front both appear upstream the cylinder. Standoff distances and induction lengths are related to reduced mechanisms. With increasing cylindrical diameter, standoff distances increase and induction length decrease either for ignition delay. The bow shock and flame are both pushed upstream but they are still remained in sequence. In contrast to reduced models of 16species/41steps and 15species/19steps, 53spesies/325steps model provides good accuracy and ignition covers a wide range of pressure and temperature. Three models demonstrate incompletely burning or chemical reactions in all cases except cases of cylinders with large diameters. It shows that elementary reactions reach chemically equilibrium but the reactions are not so completely. Meanwhile, the larger cylindrical diameter, the better accuracy in evaluation of reduced chemistry mechanisms.