A new chemical kinetic mechanism model of NO-CH4 interaction is adopted to simulate the reaction process of CH4 in the plug flow reactor (PRF) and HCCI engine based on the experimental verification. The initial NO mole concentration and reaction temperature are changed and the effect of NO on CH4 oxidation is analyzed. The results show that: NO mainly reacts with alkylperoxy ROO·produced in CH4 oxidative reaction, and alkylperoxy ROO · is transformed into alkoxy radicals RO ·. NO accelerates the oxidation of CH4 at low concentration. With the concentration of NO rising, its performance of speeding up fuel oxidation is inhibited. At low temperature, NO promotes oxidation of CH4. But at high temperature, due to low concentration of alkylperoxy ROO ·, NO almost loses its effects. The effect of NO on ignition delay of HCCI combustion is closely related to its concentration. The ignition delay reduces when NO is at low concentration, and the trend reducing the ignition delay slows down at high concentration. These results are mainly based on competition between R126 and R150.