In order to analyze effect of plasma assisted combustion in combustor, a cylindrical combustor model was set up by using Fluent software, and numerical simulation of plasma assisted combustion was conducted. By changing equivalence ratio, ionization degree and inlet velocity, the temperature distribution in combustor was achieved after calculation. The results indicate that plasma assisted combustion could effectively increase flame propagation velocity and combustion temperature of methane-air mixture. Non-stoichiometric ratio condition would decrease the plasma assisted combustion temperature. The effect of plasma assisted combustion is more significant under fuel-rich condition than that under fuel-lean condition. Either increasing ionization degree or decreasing inlet velocity could enhance the effect of plasma assisted combustion.