Abstract: Research on hydrogen separation processes based on diffusion methods is conducted for the gas purification step in the preparation of high-purity hydrogen. By establishing a multi-component gas separation model, the separation coefficient of hydrogen mixtures during diffusion is analyzed, and the appropriate operating conditions for a single-stage separation process are determined. The basic complete separation coefficient of hydrogen mixtures during diffusion separation is verified through experiments. Based on the single-stage experiments and the relative separation coefficient of hydrogen and nitrogen in the mixture, the relative separation coefficients of all components in the converted gas mixture are derived. Further feasibility studies are conducted on the multi-stage cascade scheme for producing high-purity hydrogen from converted gas. The study finds that a cascade of 124 stages can achieve the goal of producing 99.999% high-purity hydrogen products. The production cost per unit product is given, which is relatively competitive compared to other high-purity hydrogen production costs. The application of diffusion methods in the preparation of high-purity hydrogen has certain feasibility and application prospects.