Knock in a single-cylinder spark ignition (SI) optical engine was modeled and investigated using an improved version of the KIVA code with a G-equation combustion model, together with a reduced chemical kinetics model and an enhanced wall heat transfer model. The ERC PRF mechanism (47 species, 132 reactions) was adopted to model the end gas autoignition in front of the flame front and the postoxidation process behind the flame front in the burned zone. An improved wall heat transfer model was developed that accounts for pressure oscillations and near wall chemical heat release. The model describes end gas autoignition and the spatial distribution of intermediate combustion radicals, as well as the characteristics of the pressure wave oscillation during spark-ignition engine combustion. The predicted data agree well with available experimental results from an optical engine. The simulated results further indicate that the local in-cylinder pressure is extremely uneven during the knocking process. The pressure oscillations couple with chemical reactions simultaneously and interactively and lead to significantly enhanced heat transfer. The acoustic characteristics of SI engine knock are basically consistent with the "drum mode", and the oscillating energy is mainly focused in the first resonance mode.