This paper presents a three dimensional study of a gas-fired, regenerative, side-port glass melting furnace. The furnace is divided into three regions: combustion space, glass tank and batch blanket. The combustion space is simulated separately, while the glass tank and the batch blanket are coupled together as a whole. To couple the three regions, a new method is proposed that is more flexible and faster than the existing conventional methods. The melting process of the batch blanket, the natural convection vortices of the glass tank and the turbulence and the chemical reactions of the combustion space are all simulated. The simulation was preformed using Gambit-2 and Fluent-6 software. The calculated temperatures are compared with actual values measured at different locations on the furnace surfaces. Results indicate that the maximum relative error is less than 7.6%. This work can form the basis for the parametric analysis of the furnace to reduce its fuel consumption.