To satisfy the large stroke adaptive optical system required, we presented an analysis of an approach to improve the stroke of the deformable mirror. We discussed the influence function between the structure parameters and the main performance index by using Finite Element Analysis (FEA). In addition, the structure parameters of the mirror and actuator in a telescope adaptive optical system were discussed based on the FEA results. The results show that the stroke response of the deformable mirror could be improved with optimizing parameters based on the existing techniques.