This study integrates magnesium alloy and traditional steel into a new hybrid thin-walled, double-hat-shaped hybrid tube to improve crashworthiness. Two classes of hybrid tubes are examined, namely, Hybrid-I(steel top hat and magnesium-alloy bot- tom hat)and Hybrid-II(magnesium-alloy top hat and steel bottom hat).The energy-absorption characteristics and crashworthiness op- timization of the thin-walled hybrid structures are investigated under three-point bending conditions through experiments and simula- tions. The multi-objective optimization design for the two kinds of hybrid tubes is implementedto elucidate the hybrid tubes lightweight properties. Results showed that Hybrid-I tube has better crashworthiness and lightweight properties compared with Hybrid-II tube. Hybrid-I tube also has better lightweight properties than single-material steel tube and reduced wall thickness compared with mag- nesium-alloy tube.