Plasma-assisted combustion is the frontier research in the field of energy and power. In order to reveal the mechanism of plasma-assisted combustion, the mechanism of plasma excitation on CH4/Air combustion reaction is studied. Using the CHEMKIN, a CH4/Air discharge model and a zero-dimensional dynamic calculation model of plasma-assisted CH4/Air combustion are established. Through the simulation calculation, the ignition delay time, the evolution law of the active particle concentration, the chemical reaction path and the consumption of OH, and the sensitivity of the elementary reactions are obtained. The results show that during the CH4/Air mixed gas discharge breakdown, a large number of excited-state particles are generated, in which N-2(ap) reacts most strongly with CH4 to promote the reaction. The dissociation effect of N-2(C-3) on CH4 is most prominent in the combustion reaction. In addition, it is found that adding plasma, increasing ignition temperature and increasing reaction pressure can shorten the ignition delay time and increase the upper limit of temperature rise. In the combustion reaction, H + O-2 = O + OH play a major role in promoting the reaction.