A high-efficiency isolated DC-DC converter based on a coreless micro-transformer was designed using the GSMC 0.35 μm BCD process. The effects of line width, inner diameter, line spacing, number of turns and distance between primary and secondary coils on the efficiency of isolated DC-DC converter are analyzed, and a set of coreless miniature transformer models with the best EMX modeling and simulation data are applied to the isolated DC-DC converter. Finally, the optimal coding and decoding scheme is selected. Further improve the conversion efficiency of the converter. Simulation results indicate that at a working frequency of 180 MHz, with an input supply voltage of 5 V and an output isolated voltage of 5 V, the converter can output a current range of 0 to 120 mA, with a maximum output power of 600 mW and a peak conversion efficiency of 40%.