Some kinetic parameters have been determined in this work for thermal and catalytic cracking of the mixed of polyethylene and polypropylene using batch method. The cracking reaction was carried out at different temperature 470,490 and 510oC under atmospheric pressure. The mass of products (liquid and gas fractions) were determined and used to plot the curves of the thermal and catalytic decomposition. We used two types of catalysts: Syrian natural Zeolite and the same after loading with sulfate ions using impregnation method. The thermal cracking has a long time and has firs-pseud order reaction. While in the case of catalytic process we note that the reaction finished in the short time and the process is the Zero-pseud order reaction. The rate of the cracking increased very much, the rate constant was k1=0.0032.min-1 in the thermal cracking at 4700C and ko=0.111.min-1 in the case of catalytic cracking in presence of Z catalyst and ko= 0.206 min-1 in presence of 15-SO4 2-/Z as catalytic at the same temperature. In the other hand activation energy was 208.7 kj/mol in the thermal process and decreased to 116.6 kj/mol at Z catalytic presence and to 87.3 kj/mol at 15-SO4 2-/Z catalytic presence.