A methodology of fluid-structure bi-directional interaction based on computational fluid dynamics/computational structure dynamics (CFD/CSD) was presented. The donor-receptor relationship between two sets of grid system was identified by alternating digital tree (ADT). The local interpolation methods were used for data exchange between these two sets of grids. Flow with moving boundaries was dealt with by Delaunay graph mapping method. The code for nonlinear structural finite element and information transfer was developed and used to connect with the code of flow solver 3D2MUFS developed in the Micro Air Vehicle Center of Nanjing University of Aeronautics and Astronautics (NUAA). It was applied to the aerodynamic computation of dragonfly flapping flight with flexible wing. Results show that the time-averaged vertical force coefficient of the dragonfly wing increases from 0.31 to 0.53

and the time-averaged thrust coefficient increases from 0.07 to 0.13 by flexible deformation. This confirms that the flexible deformation can improve the aerodynamic performance of flapping wing.