The invention discloses a corrugated-steel-plate lining arch-foot structure of a railway tunnel and an optimal design method of the arch-foot structure. The structure comprises arch-foot foundation structure bodies and a plurality of foot-locking anchor rods, wherein the arch-foot foundation structure bodies are located at two arch feet of an arch-shaped corrugated-steel-plate lining respectively;the arch-foot foundation structure bodies are reinforced concrete structures and are longitudinally arranged along the corrugated-steel-plate lining; the arch feet of the corrugated-steel-plate lining are anchored with the corresponding arch foot foundation structure bodies; one end of each foot-locking anchor rod is inserted into an anchor hole of a tunnel wall, the other end of each foot-locking anchor rod is anchored with the corresponding arch-foot foundation structure body, and the foot-locking anchor rods are longitudinally distributed along the corrugated-steel-plate lining. Accordingto the corrugated-steel-plate lining arch-foot structure of the railway tunnel and the optimal design method of the arch-foot structure, reinforcement of the foundation structure bodies and quantitative design of the foot-locking anchor rod parameters are achieved by defining the external load of the foundation structure bodies, the whole design process is quantitative, clear, convenient to implement, safe, reliable, economical and applicable, original secondary lining and chiseling construction is avoided, the construction risk is reduced, the construction cost is saved, and the constructionperiod is shortened.