Abstract: In order to explore the effect of flexibility on the aerodynamic performance of dragonfly forewing when flapping forward, this paper is established the forewing model according to the actual parameters of dragonfly, and put forward two flexible distribution modes along the chordwise, which are uniform flexibility distribution and variable flexibility distribution. Firstly, the overlapping grid and bidirectional fluid structure coupling technology are used to realize the fluid structure coupling of the dragonfly forewing in the flapping process by STAR-CCM+. Secondly, then the non-uniform flexible distribution of the forewing is realized by changing the young's modulus function in the solid region of the dragonfly forewing. According to the calculated results, it can be concluded that under the condition of uniform flexible distribution, only when the young's modulus is small, the change trend of the lift coefficient and drag coefficient curves of the flexible wing lags behind the half period of the rigid wing and further added more drag to the flight. However, with the gradual increase of Young's modulus, the drag of the dragonfly forewing decreases, the thrust increases, and the momentum increment, acceleration and time average thrust coefficient given by the thrust to the dragonfly forward flight first increase and then decrease. Under the condition of reasonable non-uniform flexible distribution, the flexible wing significantly improves the peak thrust coefficient and time average thrust coefficient. When flying forward, the dragonfly forewing is given a large momentum increment and acceleration. Compared with the rigid wing and the dragonfly forewing with two flexible distribution modes, the dragonfly forewing can obtain better aerodynamic performance when the flexibility is non-uniform flexible distribution.