This study focused on the seismic performance evaluation of high strength sandwich composite members. A series of combined loading tests on members with various sectional compositions were conducted to investigate the relationship between the sections’ void ratios and the members’ strength, stiffness, and ductility. It was found from the test results that the strength and ductility of sandwich members with adequate sectional void ratios were higher than those of concrete-filled tubes with similar dimensions. Test results also showed that the members’ deformation and energy dissipation capacities decreased when the sectional void ratios increased. It was further validated from response comparisons that the members’ stiffness deterioration rates were larger when the members’ sectional void ratios increased. A simplified expression for member stiffness evaluation was proposed for engineering practice references.