According to the requirement of prediction of dynamic stability and recovery and landing of hypersonic inflatable aerodynamic decelerator, this paper presents a detailed analysis of structural deformation effect on the dynamic stability for the decelerator in the most sensitive velocity range of Ma=0.15 to 4.6. The flow field and aerodynamic coefficients of the aircraft with and without structural deformation are obtained with a Reynolds average Navier-Stokes equation solver. Steady simulation results shows that the static structural deformation results in local flow separation on the winward surface of the aircraft and increases the axial aerodynamic coefficient. Unsteady simulation results of forcing pitching oscillation and rigid moving mesh technique show that the high pressure on winward surface stablizes the aircraft dynamic stability while the vortex in the wake flow weakens the vehicle dynamic stability, the axial symmetric structural deformation enhances the decelerator dynamic stability in total.