A single-phase three-level AC/DC resonant converter is designed to achieve a high power density and operate over a wide output voltage range (200Vdc-430Vdc). In order to further improve the power density of the converter, a passive integration is proposed with flexible multi-layer foil (FMLF) integration technique in this paper, which includes two filter capacitors, two Boost inductors, two series resonant capacitors, two series resonant inductors and two transformers. The composition principle, magnetic flux analysis and parameter design of the proposed integrated unit are introduced in detail, respectively. A Maxwell/Ansoft simulation model is built for a 1.5kW-110kHz single-phase three-level AC/DC converter to verify the feasibility of the proposed integrated unit.