By solving the two dimensional Navier-Stokes equations,a numerical study on the effect of flapping wing deformation on aerodynamic forces is carried out while the wing is in hovering flight,and the variations of aerodynamic forces and flow patterns around the flapping wing with the wing deformation are examined.The results show that the flapping wing provides a higher lift force when it is in an appropriate deformation and hence gives better aerodynamic performance than a rigid one.However,an excessive deformation of the wing may make the aerodynamic performance of the wing worse.