Wind turbines used in the conversion of wind energy into useful energy consist of different aerofoil models. One of the most important factors affecting turbine performance is the change in aerodynamic performance of the aerofoil model. The aerodynamic performance of the NACA-0018 aerofoil model, which is likely to be used in wind turbine blades, has been investigated numerically and experimentally. Numerical studies for performance analysis were studied using ANSYS Fluent (TM) 14,5 software, which is based on computational fluid dynamics (CFD), using SST (Shear Stress Transport) turbulence model. In numerical studies, Reynolds (Re) number was accepted as 5,7x10(4), and the analyses were repeated for every 2,5 degrees angle of attack from 0 degrees to 60 degrees. Experimental studies were carried out in the open loop wind tunnel between 0 degrees-60 degrees for every 5 degrees angle of attack. In both studies, the lift coefficient (C-L), drag coefficient (C-D) and aerodynamic efficiency (C-L/C-D) values of the NACA-0018 aerofoil model were determined for selected attack angles. According to the numerical results, a stall occurred at 32,5 degrees angle of attack for the AR1 model, while at 25 degrees for the AR2 model. Considering with the results of experimental study for AR1 and AR2, the CL value of both models was 0,41% and 2,71% better than the data obtained as a result of numerical studies, respectively. Similarly, it was concluded that the experimentally obtained CD values were 6.35% and 5.16% better than the numerical data for the AR1 and AR2 models, individually. As a result of numerical study, the C-L/C-D values obtained for AR1 and AR2 were 3.86% and 12.04% higher for each aerofoil model than the experimental data for the same structures. As a consequence of both experimental and numerical study, the aerodynamic efficiency of the AR1 structure from the structures of NACA-0018 aerofoil models having two different aspect ratios had a significant advantage compared to the AR2 before and after the stall. stall.