Abstract: This paper used numerical methods to investigate the flow field around wind turbine airfoil S809 and the airfoil with micro tab at 95% chord at the pressure side neat the trailing edge. The adaptive SST turbulence model was chosen to analyze the detailed flow field of the two airfoils under different angles of attack. The effect of the micro tab was brought out, and then the lift arising mechanism of the micro tab was presented. The results showed that the lift arising mechanism of the micro tab lied on the change of Kutta condition of the airfoil. The micro tab made the stagnation point move to the end of the micro tab, which made the aerodynamic profile and circulation increased. Meanwhile, the micro tab only availed at the normal working condition.