In the present investigation, the effect of different Gurney Flaps (GF) heights ranging from 0.25% C to 5% C on the performance of NACA 0012 is analyzed and the optimum is chosen from this investigated height. Use to estimate the flow structures around the airfoil turbulence model k-ω (SST) shear stress transport equations are employed. The present results showed that gurney flap improves not only the lift but also increases the ratio of lift to drag ratio at the different angles of attack ranging from 2°,4°,6°, 8°, to 10°. The pressure distribution around the airfoil is presented which is useful to comprehend the technique of gurney flap on airfoil aerodynamic performance. Moreover, it is found that the increase of airfoil drag with gurney flap can be Increase to the increase of pressure drag between the windward and the leeward sides of the gurney flap itself. the tide of a gurney flap for a height of 1.5% chord at the trailing edge give the optimal performance as the lift to drag ratio increased at all angles of attack consequently; therefore it is recommended to install GF with a height of 1.5% chord to the trailing edge to obtain maximum lift enhancement with a minimum drag penalty