The reversible solid oxide fuel cell (RSOFC) is a promising solution for future storage system in power grid, but the wide voltage range makes it difficult to design the DC/DC converter for RSOFC stack. In this paper, the losses of two DC/DC topologies, CLLC cascade interleaved Buck (two-stage) converter and dual-active-bridge (DAB) converter, are compared as the interface DC/DC converter for RSOFC. Firstly, the topology and control method is introduced for two selected DC/DC converters. Secondly, the losses of two converters are analyzed and corresponding loss models are presented. The loss models are also extended for multi-port topology. At last, based on 1 kW single port prototype, the experiments are conducted and the total loss are measured for two topologies. Both the model and experimental results indicate that the two-stage topology has higher efficiency and is selected for the interface DC/DC converter for RSOFC stack.