An engine control system for controlling an engine into which fuel is supplied from a fuel supply system and which is ignited by an ignition system, the engine control system comprising: a detonation detecting device for detecting detonation of said engine; a judgment level setting device for setting a judgment level for judging whether detonation, which requires to be controlled, occurs; an enrich controlling device for controlling the fuel supply system so as to vary, to a rich-side, air-fuel ratio of air-fuel mixture being supplied to the engine for controlling the detonation when a level of an output signal of the detonation detecting device is equal to or more that the judgment level; and an ignition controlling device for controlling the ignition system so as to intermittently stop an ignition operation of the engine when the detonation can not be controlled by the enrich controlling device.