As shown in Figure , the Gas-to-Liquid (GTL) process is modelled in Aspen Plus, containing combined reforming, FT synthesis, and product upgrading section. This process starts with the combined reforming (CO2 + H2O) of natural gas to syngas, followed by FT synthesis for fuels. Since the upgrading section has little influence on the overall performance, we use a distillation column to simplify it. In this work, more attention is given to the reforming and FT, as well as the flowsheet building in Aspen Plus and its simulation convergence.