To improve and enhance the lightweight and safety of automotive seats, carbon fiber and glass fiber hybrid reinforced plastic (C-GFRP) are used to replace the steel structure of the front seat backrest of a certain model of the automobile, and a design strategy based on the orthogonal experimental design method combining entropy weighting method and grey correlation analysis of the composite seat backrest is proposed. A variety of different paving structures were designed for C-GFRP based on factors such as ply orientation angle, thickness, and sequence, and the weight coefficients of each response index were calculated by entropy weight method through comparison of the 50th percentile dummy rear-crash conditions and modal analysis. Multi-objective ply optimization was performed by grey correlation analysis to obtain the optimal ply scheme. The results show that compared with the original steel backrest seat, the designed carbon-glass hybrid fiber composite backrest seat has improved performance in all aspects, and the mass has been reduced by 61.2%, which is a significant weight reduction effect.