The proposed soft-switching DC/DC converter includes: a basic non-isolated DC/DC converter having an inductor, and an auxiliary switch module including: an auxiliary switch having a first terminal electrically connected to a first terminal of the inductor, a second terminal, and a control terminal, a resonant inductor having a first terminal electrically connected to the second terminal of the auxiliary switch, a resonant diode having a cathode electrically connected to a second terminal of the resonant inductor and an anode electrically connected to a second terminal of the inductor, and a main switch. A driving signal is input to the control terminals of the main and the auxiliary switches from a driving circuit to switch the main and the auxiliary switches at a zero-voltage and a zero-current so as to have zero switching loss respectively.