In this paper, the optimization of typical reaction variables for a pilot scale synthesis of carbon nanofibers (CNFs) Using a fixed-bed reactor has been carried out to provide it more economically viable large scale production of these materials. Using a Ni/SiO2 catalyst (10 wt % Ni) and ethylene as the carbon source, the optimum value of temperature, space velocity, and H-2/C2H4 ratio (v/v) in terms of carbon yield was 600 degrees C, 10000 h(-1), and 1:4, respectively. The modification of these variables caused a significant change in the type and amount of solid carbon recovered. Carbon product characterization demonstrated that CNFs with mesoporous character, large external surface, and good thermal stability and crystallinity were obtained. Finally. results demonstrated a Successful scale-Lip by a factor of 45 in the pilot plant scaled a CNFs yield of 106 g(CNFs)/g(catalytic metal) could be obtained at optimal conditions during a reaction time of 60 min at optimal conditions in the pilot plant scale. For the same reaction conditions, Only 80 g(CNFs)/g(catalytic metal) were obtained in the laboratory reactor.