This research focused on the design and optimization of a two-phase Fischer-Tropsch (F-T) reactor in a gas-to-liquid (GTL) process. For the design of the F-T reactor, the overall process configuration was developed using Aspen HYSYS software. Various reaction mechanisms for the F-T process over iron-based catalysts were reviewed from the published literature. The F-T kinetics was adopted for reactor modeling, and the reaction kinetic parameters were adjusted to increase the accuracy of the modeling results. Furthermore, the effects of catalyst size, catalyst active sites, and reactor configuration were embedded into the modeling. The yields of the F-T process were analyzed under various operating conditions. Finally, operating conditions, such as the temperature and pressure of the two-phase-reactor model, were optimized to maximize the yield of hydrocarbon products.