The invention discloses a control method based on a cascade bidirectional DC-DC converter. The method is relatively simple; and by means of controlling a capacitance voltage through a control unit to be equal to product of a first power voltage and a turns ratio N of a transformer coil, the method can realize soft switching of all switching devices of the cascade bidirectional DC-DC converter in a full-load range. Meanwhile, while transmitting the same power, effective value of resonant inductor current of the cascade bidirectional DC-DC converter can be minimal. Overall efficiency of the cascade bidirectional DC-DC converter is improved.