The embodiment of the invention discloses a bidirectional DC/DC converter, and a bidirectional voltage converting method, device and system. The bidirectional DC/DC converter comprises a direct current supporting capacitor unit, a first bidirectional DC/DC unit and a second bidirectional DC/DC unit, wherein one end of the direct current supporting capacitor unit, a first end of the first bidirectional DC/DC unit and a second end of the second bidirectional DC/DC unit are connected with a first positive direct current bus; the other end of the direct current supporting capacitor unit, a third end of the first bidirectional DC/DC unit and a first end of the second bidirectional DC/DC unit are connected with a first negative direct current bus; a second end of the first bidirectional DC/DC unit is connected with a second positive direct current bus; a third end of the second bidirectional DC/DC unit is connected with a second negative direct current bus. Through the bidirectional DC/DC converter, the bidirectional voltage converting method, the bidirectional voltage converting device and the bidirectional voltage converting system, the voltage converting efficiency can be improved, and the buck-boost capability of the bidirectional DC/DC converter can be improved and the cost of the bidirectional DC/DC converter can be reduced.