The effect of surface local vibration excitation on the aerodynamic characteristics of SD8020 airfoil under small angles of attack is studied by numerical simulation at Re=4×10⁴. The influence of vibration frequency and amplitude on the flow characteristics of airfoil is studied from time averaged and unsteady aspects. The results show that local vibration at 2° and 3° can effectively affect flow field， promote the transformation of the laminar separation bubble structure and improve the aerodynamic performance of the airfoil. It is found that the effects of vibration frequency on aerodynamic characteristics and flow field structure of airfoil are similar under different angles of attack. When f=32 Hz， the improvement of aerodynamic characteristic is the most effective. With the increase of the vibration amplitude， the separation bubble structure span becomes smaller and moves towards the leading edge. The further unsteady analysis shows that the evolution process of unsteady vortex presents the similar mode under the same control strategy. And pressure pulsation frequency at chordal position is consistent with the vibration excitation frequency. It can be found that the unsteady characteristics of the flow field are dominated by the vibration excitation under this research condition.