High load performance and fuel economy of gasoline engines are limited by knocks. Such limitations are becoming worse when the engine is heavily super-charged for high BMEP outputs. Spark ignition timing retardation has been an efficient method to avoid knock but results in reduced engine performance and poor fuel economy. A better understanding of knock, which could be used to optimize the engine design, and ignition timing optimization in particular, is important. In this research, a simulation model for SI engine knock has been developed. The model is based on a three-zone approach (i.e., unburned, burning, and burned zones). Tanaka's reduced chemical kinetic model for a commercial gasoline fuel with an RON of 95 has been modified and applied in both burned and unburned zones incorporated with the LUCKS (Loughborough University Chemical Kinetics Simulation) code. Both post-flame heat release and pre-flame autoignition have been simulated. The burning zone uses equilibrium combustion thermodynamic models. The simulated results have been validated against experimental results, and good agreements have been achieved.