Present-day there are two of theories which have considerable scientific support to explain the knock phenomenon in S.I. engine, the detonation theory and the autoignition theory. But they still have some problems to explain effects of knock parameters, i.e.. compression ratio, spark timing, mixture quality, engine speed, ect, on knocking process in S.I. engine. Accordingly, it is essential to find out whish is more adequate theory of two and to develop the method of analyzing knock phenomenon, that is the aim of this paper. The Authors develop the method of predicting transient temperature and pressure at the end-gas zone during the combustion period and analyze knocking process by this method based on the knock theories. The caluculated values based on the autoignition theory show reasonablly correct relations between knock parameters and knock process but there is no evidence of knock occurred by detonation theory through the calculation according to the all parameters. The authors find out that the autoignition theory is more adequate than detonation theory to analyze knocking process in S.I. engine.