Abstract: Auto-ignition is an essential phenomenon in enginecombustion process, whichis controlled by chemical kinetics. The concept of knock integral approachproposed by Lenvingood and Wu is verified by the author's research on sketch kinetics of n-heptane. It is shown that during the auto-ignitionof fuel, the radical OH plays an important role. Only if the heat release and COin the low temperature reaction are accumulated to a certain level, atwhich the reaction H+O_2 = O+OH can take place and the concentration of radical OHincreases rapidly to transfer CO into CO_2 and with more heatrelease, the auto-ignition occurs. The advanced combustion technologybased on the concept of auto-ignition control in engines is discussedin this paper.