The invention provides a novel busbar-free four-port bipolar DC-DC (direct current to direct current) converter which comprises an annular architecture. The annular architecture is formed by four converter unit groups in sequential connection; each converter unit group comprises two converter units in connection; each of two power electronic device branches of each converter unit comprises two power electronic devices in same-direction connection; junction points of the power electronic devices are connected through electric reactors. Compared with the prior art, the novel busbar-free four-port bipolar DC-DC converter has a power bidirectional flow capability and is applicable to different operating conditions of a direct-current system, power conversion coefficient is decreased, and power conversion efficiency of the converter is improved.