Hydrogen, as a zero-carbon energy carrier and chemical raw material, plays a critical role for China to realize its peak carbon dioxide emissions, carbon neutrality goals (“dual carbon” goals) and develop a low-carbon, green modern energy system. Among the many factors constraining the industrial application of hydrogen energy, long-distance hydrogen transmission is a key challenge. Leveraging on existing mature natural gas pipeline transmission technology and well-established natural gas pipeline infrastructure, hydrogen-blended natural gas pipeline transmission holds promise for realizing long-distance, large-scale, and low-cost hydrogen transmission. This paper first provides an overview of the feasibility, application, and demonstration projects of hydrogen-blended natural gas technology. It then discusses the application of pressure swing adsorption, membrane separation, and their coupled processes for the separation and purification of hydrogen from blended natural gas. Finally, based on the Sichuan-to-Eastern China Gas Transmission Pipeline, the cost of transporting and purifying H2 is estimated to be 14.89 yuan/kg. This research provides theoretical guidance for the development of hydrogen-blended natural gas technologies.