Abstract: Steel frame structures with sandwich composite panels (SCPs) have been widely applied in engineering practice. Connections between the steel frames and SCPs impose significant influence on the seismic behavior of the entire structure system. To investigate the failure modes and force mechanisms of the connections, five one-bay steel frames with SCPs were tested under cyclic loads. The skeleton curves of the connections and the entire structure were compared in order to analysis the stress strain curves of panels, embedded parts, steel wire and concrete. Results show that the connections have sufficient bearing capacity and provide effective connection to the steel frames and panels; the embedded parts ensure the synergy between the steel frames and panels, and the oblique cross steel plates improve the ultimate bearing capacity of the entire frame and the connections and the synergy between the steel frames and panels. This study lays a solid foundation for the engineering application of structure systems of this kind.