This paper presents a bidirectional DC/DC phase-shift full bridge (PSFB) converter and the related modulation strategy. The proposed solution retains the ZVS characteristics of a traditional phase-shift full bridge converter when its power flow direction is positive. Besides, the proposed solution obtains ZCS characteristics on the primary and secondary side with the help of the proposed modulation strategy when its power flow direction is negative. So the high efficiency performance can be got, no matter which power flow direction is. Furthermore, the gain ratio, soft switching condition in negative power flow direction case are analyzed. Finally, the simulation results validate the theoretical analysis.