One of the most critical components of gas turbine engines, rotor blade tip and casing, is exposed to high thermal load. It is a significant challenge to the designer to protect the turbine material from this severe situation. A single stage gas turbine engine was modeled and simulated using commercial CFD solver ANSYS CFX R.11. The modeled turbine stage has 30 vanes and 60 blades with a pressure ratio of 3.2 and a rotational speed of 9500 rpm. The predicted isentropic Mach number and adiabatic wall temperature on the casing showed good agreement with available experimental data under the close operating condition. The effects of tip clearance heights and rotor speeds have also been analyzed and compared one with respect to others. Same typical patterns of leakage flow structures and heat transfer rate distribution can be obtained in both steady and unsteady simulations. However, steady simulation underpredicted the highest heat transfer rate. Because it couldn't capture the critical local high heat transfer phenomena caused by the unsteady stator-rotor interactions.