It is of more significance for improving the prediction accuracy of aircraft aerodynamic performance to predict the transition position of the boundary layer accurately. Selecting the model coupled with SST k-w turbulence model and taking no-pressure-gradient plane as an example, the capability of this model for trapping flow transition automatically was verified. Then the model was applied to study the flow characteristics and aerodynamic performance of NACA 0012 airfoil with pressure gradient, the results from which were compared with the computational result from original SST k-w model and the test data of complete turbulence model. The study shows that the transition position of airfoil surfaces predicted by the model and even the drag coefficients are very good as the angle is less than 12°. While there is a very big deviation as the angle is equal to or bigger than 12°, the reason of which may be that two-dimensional method can not catch three-dimensional effect and unsteady characteristics of separation on airfoil surfaces.