Abstract: To obtain a better view on the effect of steam reforming of methane (SRM) reaction on performance of internal combustion (IC) engine, by using HSC 5.1 software, SRM was analyzed at different temperature and steam/methane molar ratios. Then, by using Chemkin-pro software, fuel consumption reduced rate of methane was calculated in synthesis gas of SRM and methane at different equivalence ratios. The results show that the increase of temperature and steam/methane molar ratios will increase conversion rate of methane. When the temperature is 700 ℃ and steam/methane molar ratio is 3 under the same heating conditions, heat value will increase 13.58%, fuel consumption will decrease 11.96%, and cycle efficiency of IC engine will increase with the increase of conversion rate of methane. Efficiency of synthesis gas of SRM is higher than pure methane, unfortunately, decreases with the decrease of the equivalent ratio.