In this study the catalytic behavior of Co/HZSM-5 in Fischer-Tropsch synthesis (FTS) has been examined in order to optimize the operating conditions for acquiring maximum selectivity. Catalysts consisted of various quantities of cobalt particles supported on HZSM-5 zeolite were prepared by impregnation method. In order to investigate the effects of operating parameters on catalytic performance and to estimate the optimum conditions, experiments were designed using L-16 Taguchi method. All experimental runs were carried out in a fixed bed reactor under isobaric condition (2 MPa). According to the Taguchi model and considering the impact of the operating parameters on the process output and performing certain validation tests, the optimum operating conditions for the process were determined as T = 513 K, space velocity = 1.1 h^(-1), Co on HZSM-5 = 11.6%, H2/CO = 1.7. In the next step, a kinetic model for FTS based on carbide mechanism was presented applying the synthesized catalyst under the optimum conditions. This model is a combination of kinetic rates of hydrocarbon formation and the relations for the growth probability and olefin re-adsorption factor.