In order to imitate the seagull flying, a two stage bionic flapping wing mechanism was designed. The simplified model of single crank double rocker mechanism was established, and the empirical formulas of each rod length satisfying the minimum deviation angle of two rockers were analyzed. The dynamics model of flapping-wing aircraft was established by using SolidWorks and ADAMS software. The motion parameters of internal and external wings and the overall position and attitude changes of the aircraft were analyzed. The results show that the mechanism with angle between the crank and the left rocker has more advantages in reducing the phase difference angle between the left and right rockers under the same length of the rod.The mechanism design is reasonable，which provides reference for flapping-wing aircraft in the following study．