In this study, the glass fiber drawing from a silica preform in the furnace for the optical fiber manufacturing process is numerically simulated by considering the radiative heating of cylindrically shaped preform. The one-dimensional governing equations of the mass, momentum, and energy conservation for the heated and softened preform are solved as a set of the boundary value problems along with the radiative transfer approximation between the muffle tube and the deformed preform shape, while the furnace heating is modeled by prescribing the temperature distribution of muffle tube. The temperature-dependent viscosity of silica plays an important role in formation of preform neck-down profile when the glass fiber is drawn at high speed. The calculated neck-down profile of preform and the draw tension are found to be reasonable and comparable to the actual results observed in the optical fiber industry. This paper also presents the effects of key operating parameters such as the muffle tube temperature distribution and the fiber drawing speed on the preform neck-down profile and the draw tension. Draw tension varies drastically even with the small change of furnace heating conditions such as maximum heating temperature and heating width, and the fine adjustment of furnace heating is required in order to maintain the appropriate draw tension of 100~200 g.