Studying　the　synergistic　effects　of　dilution　gases　and　hydrogen　on　the　laminar　combustion　characteristics　and　NOX-emission　X-emission　concentrations　of　methane/air　can　contribute　to　achieving　efficient　and　clean　natural-gas　combustion.　This　study　quantitatively　analyzes　the　impact　of　N2　2　and　CO2　2　as　dilution　gases　on　the　laminar　combustion　characteristics　and　NOX　X　emissions　of　methane/air　under　different　equivalence　ratios.　The　virtual　gases　FN2　2　and　FCO2　2　are　introduced　to　distinguish　between　the　physical　and　chemical　effects　of　the　dilution　gases.　Subsequently,　the　effect　of　hydrogen　addition　on　the　laminar　combustion　characteristics　and　NOX　X　emissions　of　a　methane/5%　dilution　gas/air　mixture　is　investigated.　Finally,　the　synergistic　effects　of　the　dilution　gases　and　hydrogen　on　the　laminar　flame　speed　and　NOX-emission　X-emission　concentrations　of　methane/air　under　various　blending　conditions　are　discussed.　The　results　indicate　that　CO2　2　exhibits　a　more　substantial　reduction　in　laminar　flame　speed,　flame　temperature,　key　radical　concentrations,　and　NOX-emission　X-emission　concentrations　than　N2,　2　,　primarily　because　of　its　physical　effects.　N2　2　has　minimal　chemical　effects,　but　marginally　increases　NOX　X　emissions.　The　addition　of　hydrogen　increases　the　laminar　flame　speed　and　key　radical　concentrations　of　the　methane/dilution　gas/air　mixture.　however,　significant　differences　in　the　NOX-concentration　X-concentration　trends　with　increasing　hydrogen-blending　ratios　are　observed　for　the　three　equivalence　ratios　(Phi　=　0.7,1.0,1.4).　Selecting　appropriate　blending　ratios　of　dilution　gases　and　hydrogen　can　simultaneously　enhance　the　laminar　flame　speed　of　methane/air　while　reducing　the　NOX-emission　X-emission　concentrations.　This　study　provides　valuable　insights　into　the　optimization　of　the　blending　ratio　of　hydrogen-enriched　natural-gas　engines　coupled　with　exhaust-gas　recirculation.