The maximum reaction rate arrival time (TMR_{ad}) is a very important parameter in chemical process thermal risk assessment. The general method for calculation of TMR_{ad} is based on N-order model kinetic analysis. However, the chemical reaction process is so complicated that only do kinetic analysis based on N-order without consider the type of reaction may cause large deviation or even incorrect assessments. Therefore, this paper proposes to calculate TMR_{ad} and *T*_{D24} by numerical calculation methods based on reaction model. 20% DTBP toluene solution and CHP represent N-order reaction and autocatalytic reaction, respectively. The analysis of ARC test data of two substances shows this method can be used to calculate TMR_{ad} and *T*_{D24} of N-order reaction reliably, but the comparison of autocatalytic reaction with two methods shows that although the fitting effect is very good, the general method calculated result has a large deviation, because the kinetic parameters are different under two models, this paper also perform the deviation size analysis. Therefore, it can be seen that the numerical calculation method has wide-range applicability, and to an exothermal curve, it is necessary to use the method to evaluate the TMR_{ad} and *T*_{D24} based on the understanding of the reaction type, so that the evaluation result is more reliable and accurate.