Numerical simulation of the non-premixed combustion of methane air mixture in a gas turbine can- type swirl combustor is conducted. The study objective is to examine the effect of different design and operational parameters on the combustor performance and its emissions. The investigated parameters are the primary air flow rate, the swirl ratio between the secondary and the primary air and the fuel to the primary air swirl ratio. Several indicators are used to evaluate the combustion performance and emissions which include average exit temperature of the chamber, pattern factor, NOx and CO emission indices, combustion efficiency and the pressure drop. The results of the study demonstrate the importance of good tuning of the design and operating parameters for better performance and reduced emissions