This paper focuses the computational fluid dynamics analysis inside the gas turbine combustor for the combustion of biodiesel and air mixture. The biodiesel (methyl soyate) is made from the vegetable oil (soybean oil). ANSYS fluent is used for Numerical simulation and model adapted Eddy dissipation concept for turbulence, discrete model, k-epsilon (standard), and the species transport. The model was validated and the combustion performance of biodiesel is predicted with an air-assist injector. The fuel spray is created by commercially available airblast atomizer in this study. The strength of recirculation increases with increased in equivalence ratio. The strong corner recirculation was observed at 0.75 equivalence ratio. The higher turbulence kinetic energy is found at the middle of the combustor. The temperature increases with the increase in the equivalence ratio in the flame stable region while it decreases with increases in the equivalence ratio. It was observed that an increase in the equivalence ratio, flame length increases. The profiles of carbon monoxide (CO) and nitric oxides (NOx) emissions can be obtained at 15% atomizing airflow rates, while the total airflow rate kept constant. The NOx and CO emissions are effected mainly by the fuel-air mixing process that the fuel-air mixing process and atomization have the great impact on CO and NOx emissions.