Abstract: In this paper,three symmetric airfoils with different thicknesses,NACA0012,NACA0015 and NACA0018,are used to study the transition problems of airfoils. The numerical simulation method based on the TSST turbulence model,the turbulence intensitybased turning judgment method and the study of the turning law of the airfoil surface flow under five large Reynolds number conditions are presented,and new reference ideas for wind turbine blade design are provided. The investigation shows that the transition judgment method based on turbulence intensity is practical and feasible. The effect of pre-transition flow disturbance can be effectively avoided by observing the transition using the step phenomenon of turbulence intensity profile on the airfoil surface. Moreover,the variation of turbulence intensity can be used to find the optimal design parameters for wind turbine blade design. It is found that the increase of the attack angle and Reynolds number cause the transition position of the upper airfoil surface to shift forward and the lower airfoil surface to move backward. In addition,the flow before the airfoil transition gradually stabilizes as the angle of attack decreases,the Reynolds number increases,and the airfoil surface thickness increases.