Compared to the traditional low-power resonant converters, the current-feed single-switch (CFSS) resonant converter has many advantages, such as lower switching loss, higher power efficiency and mitigation of oscillations. In order to improve the power density of the CFSS resonant converter, a passive integrated unit with flexible multi-layer foil (FMLF) integrated technique is proposed in this paper. In addition, the structure, flux analysis and parameter design of the integrated unit are also introduced. Finally, a simulation model based on Maxwell/Ansoft and the prototype of 80w-260khz resonant converter are established to verify the feasibility of the idea.