In this paper

Extended Huckel Molecular Orbital Theory (EHMO) and Complete Neglect Differential and Overlap Method (CNDO/2) are used to calculate chemical reactivity indices of paraffins and their radicals. Through analysing the dependence of known elementary reaction rate constants on the chemicl reactivity indices

a method for predicting unknown kinetic rate constants is presented. By means of the method

a relation between kinetic behavior of reactants (macro-properties) and their molecular structural properties (micro -properties) is established. The method is used to predict elementary rate constants of thermal cracking of paraffins and is proved to be feasible and reliable. On this basis

PFR model and pseduo - steady - state assumption are used to describe the thermal cracking process of C4- paraffins. Michelson and pseudo -Newton methods are used to self - consistently solve kinetic differential and algebraic equations. The simulated results have good agreement with overall experimental data published in the literature. It indicates that the established kinetic model of thermal cracking of paraffins is correct and reliable.