In this paper, a reflex charging strategy with the energy recovery function for a bidirectional converter (BC) is proposed to build a novel reflex-based BC (RBC) for increasing the battery charging efficiency in an uninterruptible power supply (UPS). The proposed RBC can provide a reflex charging current profile to charge the battery to obtain a high battery charging efficiency and prolong the battery life cycle. Specially, negative pulse energy of the reflex charging current profile in the proposed RBC is recovered to reduce the battery charging dissipation. A 400W prototype is design and implemented to verify the feasibility of the proposed RBC. Compared with a typical bidirectional converter, the battery charging efficiency and the battery charging speed are improved about 10% and 8.8% by the proposed RBC, respectively.