This paper presents a computational fluid-structure dynamics coupling method of flexible wing. The computational fluid dynamics is solving RANS equations. The stiffness used in computational structure dynamics is tested by experiments. Then the aerodynamic performance of flexible wing is researched and compared with rigid wing. The results show that the lift and thrust generated by flexible wing are less than the rigid wing. Flexible wing can slower the variety of aerodynamic performance when the flight environment is changing. And flexible wing has bigger stalling angle.