In the low-speed wind tmnel testing for a twodimensional wing model, a correction to the angle of incidence is considered due to the non-uniform spanwise distribution of lift. This phenomenon is concemed with the change of the effective angle of incidence, which results from the interference between the wing tip and the tunnel wall perpendicular to the wing span. Since the change of the effective angle of incidence is connected with the induced drag according to the lifting-line wing theory, the change of the effective angle of incidence may be estimated if the induced drag could be determined by experiment. In this study, the induced drag is obtained by the difference between the total drag measured by the wind tunnel balance and the profile drag determined by the wake measurements. The result with this correction to the angle of incidence is in good agreement with reliable experimental data.