Abstract: Based on the principle that the effective values and the mean values of pitching angles are equal,the influences of the different pitching trajectories on the aerodynamic performance of semi-active flapping airfoil are studied by the numerical analysis. The result show that the change of pitching trajectory influences the performance of the semi-active flapping airfoil,which is related to the damping ratio. When the damping ratio is 2.0 or 4.0,the semi-active flapping airfoil with the sinusoidal pitching motion is higher than the semi-flapping airfoil with other pitching motions in the extraction power and extraction efficiency. When the damping ratio is 2.0,the semi-flapping airfoil with the sinusoidal pitching motion increases 3.38% and 7.89% in the power coefficient and the efficiency respectively. However,when the damping ratio is 1.0,the semi-active flapping airfoil with triangle pitching motion is the largest efficiency. The motion trajectory and damping ratio can change the size and the evolution velocity of the leading edge vortex of the semiactive flapping airfoil by the analysis of the flow fields from the different semi-active flapping airfoils.