Auto-ignition process of stoichiometric mixture of methane-air is investigated using detailed chemical kinetics in a single-zone combustion chamber. Effect of initial temperature on start of combustion (SOC). The Arrhenius expression for the specific reaction rate are calculated and auto-ignition was evaluated based on the species fractions and sensitivity analysis. Our results suggest that the SOC is directly related to initial temperature and the auto-ignition will not occur if the initial temperature low enough.