Possible pyrolysis reaction paths of cyclohexane were studied by UMP2 (FULL)/3-21G * , UB3LYP/3-21G * , UB3LYP/6-31G * and RB3LYP/6-31G * calculation. Pyrolysis mechanism of cyclohexane at high temperature ranges were studied by UB3LYP/6-31G * , data ΔE 0 θ , ΔE θ , ΔH θ , ΔG θ and ΔE 0 θ < >, ΔE θ < >, ΔH θ < >, ΔG θ < > of five reaction paths (13 reaction steps) and reaction rates at 298-1473K were obtained. The calculations show: (1) the pyrolysis temperature of cyclohexane is about 873K, and the products are 1-hexene, butadiene and butene, (2) as far as the reaction paths producing 1-hexene and producing butene are concerned, when the temperature is higher than 873K, The reaction producing butene are more feasible thermodynamically and dynamically, and the activation energy of rate-determining step is ΔE 0 θ < >=374.46kJ/mol. Furthermore, at 1473K, kinetic calculation suggests that the both reactions have almost equal reaction rates. (3) In the further pyrolysis reaction, reaction path D that produces butadiene from 2-butene is supported by kinetics, which means 1,3-butadiene is the main product. (4) At 298-1473K, for the reaction paths producing 1-hexene and producing butadiene, the former is supported by kinetics, and the activation energy of rate-determining step is ΔE 0 θ < >=374.46kJ/mol. When reaching 1473K, ΔG θ < > of the rate-determining step of reaction path producing 1-hexene (ΔG θ < >=284.19kJ/mol) is still smaller than ΔG θ < > of the rate-determining step of reaction path producing 1,3-butadiene (ΔG θ < >=313.10kJ/mol). The above results are basically in accord with mass spectroscopy analysis and GPC experiments.