As a novel class of smart materials with high flexibility and large deformation，ionic polymer-metal composites （IPMCs） exhibit exceptional electro-actuated deformation characteristics，demonstrating significant potential in flexible robotics，micro-electro-mechanical systems，and biomedical engineering. Nevertheless，their inherent nonlinear dynamic responses and complex kinetic behaviors pose substantial challenges to precise control，severely limiting their deployment in high-performance systems. To overcome this bottleneck，the present study establishes a dynamic response model for high-flexibility，large-deformation IPMCs and optimizes their transfer function based on equivalent-circuit theory. Through an in-depth analysis of the material’s nonlinear properties，a precise constitutive relationship between the physical system and the numerical model is established. To achieve model-order reduction from an infinite-dimensional to a finite-dimensional representation，identification criteria tailored to the large-deformation characteristics of the material are formulated，and three distinct identification methods are employed for systematic identification of its electro-actuated deformation behavior. Results indicate that the refined weighted-iterative algorithm offers markedly superior identification performance，achieving an accuracy exceeding 98%. Additionally，the study reveals that during electro-actuated deformation，the amplitude and phase angle of the material’s dynamic response decrease with increasing resistance but increase with increasing capacitance. The optimized model proposed herein can effectively guide the design and fabrication of IPMCs while enabling high-precision control of their large-deformation behavior. This work provides a solid theoretical foundation for the development of control systems for such materials and holds significant scientific and engineering value for advancing their flexible applications in high-performance domains.