To guarantee the practicability and reliability of an inflatable stacked antenna(ISA) applied in satellite navigation and positioning system, a research is carried out in this letter on bending deformation of flexible material on the top layer of the ISA on antenna performance. Based on the supersaturated and unsaturated phenomenon of the flexible material on the top layer of the ISA, a modeling and simulated calculation method of bending deformation is proposed for a wideband circular polarization inflatable stacked antenna operating in L-band. According to the simulated results, the characteristic of impedance match, circular polarization and directivity of the ISA are deteriorating with the increasing bending degree. The method for the analysis of the bending deformation based on the ISA can be promoted to similar research on inflatable antennas. Besides, the feasibility analysis of the ISA is provided for the application in satellite navigation and positioning system in the future.