The isomerization process is a substantial technology to produce clean fuel from linear paraffinic species existing in light naphtha. We investigated the influence of hydrocracking reactions besides the other reactions on the research octane number (RON) of the isomerization product. A reaction network and a kinetic model including fifteen lumps and sixteen reactions were developed. Several experiments were carried out in a pilot plant to estimate kinetic parameters. The accuracy of the model was evaluated by comparing the model prediction with the experimental results. The maximum RON and process yield were strongly dependent on the temperature, hydrogen to hydrocarbon molar ratio (H2/Oil) and liquid hourly space velocity (LHSV). Also, increasing the reaction temperature compensated for the negative effects of raising the LHSV and H2/Oil in RON maximization. Moreover, we concluded that the hydro cracking reactions were very effective on RON, such that they can dominate the role of the other reactions. By sensitivity analysis in this research, a rule was obtained to declare the effect of operating condition on maximization of RON and the method of revamping of naphtha isomerization reactor.