The invention discloses a wide-gain common-ground asymmetric H-bridge bidirectional DC converter for an energy storage system. Common ground of input and output of the DC converter is realized, the asymmetric H-bridge structure is adopted, all switch transistors in a topological structure adopt controlled power transistors with low on-state resistance; the DC converter stores energy and releases energy alternatively through an inductor, thereby realizing step-down and step-up; the DC converter uses marrow pulse voltage for step-down and step-up, and while large-proportion step-down and step-up are realized, power switches can operate at a non extreme duty cycle near 0.5. The bidirectional DC converter in the asymmetric H-bridge structure is formed through the controllable power switches which are easy to integrate, the volume of the converter is reduced, the power density is increased, the input and output common-ground topological structure is adopted, the duty cycle is near 0.5 in the case of wide-gain operation, and an extreme duty cycle condition is avoided.