The invention discloses an engine detonation detection method. A crankshaft phase of a detonation identification window of a current combustion cylinder is compared with a crankshaft phase of an oil-fuel injector needle-valve seating period of a next combustion cylinder; whether oil-fuel injector seating noise enters the detonation identification window of the current combustion cylinder is determined; if so, an overlapping detonation intensity Cvirkr of the current combustion cylinder is calculated by using default background noise Srkr before the detonation identification window of the current combustion cylinder comes, wherein the Cvirkr is equal to ikr/Srkr and the ikr expresses a detonation sensor signal integration value of the detonation identification window of the current combustion cylinder; and bercause the default background noise is larger than a detonation sensor signal integration value of a detonation identification window of an internal combustion cylinder normally and a detonation detection threshold value increases, erroneous engine detonation judgement caused by entrance of the oil-fuel injector seating noise into the detonation identification window of the current combustion cylinder can be reduced. In addition, the invention also discloses a preignition detection method of an engine.