<p>To simultaneously enhance the crash safety and lightweight performance of automotive rear seats, this study proposes a multi-stage integrated optimization framework for Carbon Fiber-Reinforced Polymer (CFRP) rear seat back panels. This framework is specifically developed for CFRP rear seat back panels and integrates the equivalent static load method. The design approach incorporates free-size optimization, size optimization, and layup sequence optimization to replace the conventional steel back panel with CFRP. Firstly, the crashworthiness simulation model is validated against the rear seat luggage compartment crash impact test, with experimental errors controlled within 5%, thereby confirming the accuracy of the model. Meanwhile, the equivalent static load method is employed to transform the nonlinear dynamic crash conditions into a linear structural optimization problem under static loading. Subsequently, the mechanical properties of CFRP are experimentally determined through tensile, compressive, and shear tests. In the free-size optimization phase, the layup regions are refined to meet stiffness and mass constraints. The size optimization stage identifies the optimal layup thickness while satisfying both performance and manufacturability constraints, whereas the layup sequence optimization is employed to enhance structural robustness and damage tolerance. Relative to the optimized steel back panel, the final CFRP design achieves a 7.12% reduction in mass, a 7.8% increase in the first-order modal frequency, and reductions of 1.14% and 0.93% in the maximum horizontal displacements of the headrest and backrest, respectively. This multi-stage optimization strategy offers an effective and systematic approach to achieving lightweight design while maintaining crash safety, thereby underscoring its applicability in advanced automotive seat engineering.</p>