Three-port DC/DC converter (TPC) can be applied in renewable power systems and electric vehicle power systems. Three-port DC/DC converter is consisted of uni-directional DC/DC converter and bidirectional DC/DC converter, and has the advantages such as simple structure, lower cost and more flexible control. This paper proposes a family of high transformer ratio three-port DC-DC converter according to TPC classification and composition rules. The new three-port DC/DC converter is consisted of switched capacitor circuit, bootstrap circuit, BUCK and BOOST circuit. The new converter has the advantages such as high transformer ratio, flexible structure and wide range of voltage regulation, etc. It can be well applied in the new energy power generation system. Finally, experimental results verify the analysis of the new topology.