Abstract: Hydrogen energy is recognized as a clean energy, and mixing hydrogen into natural gas pipeline is an effective way to transport hydrogen on a large scale. However, as the physical properties of hydrogen vary greatly from those of natural gas, the quality of natural gas will change after mixing. Here, summary was made for the research progress of the interchangeability of hydrogen-mixed natural gas, the adaptability of the hydrogen mixing process system of natural gas pipeline, and the safety of pipeline equipment during the transportation of mixed hydrogen in the natural gas pipeline transportation system in the world. Giving consideration to the actual condition of China's gas pipeline network, it is suggested that: (1) Study should be performed on the requirements of different regions and different types of gas appliances on the interchangeability of hydrogen-mixed natural gas, and evaluation should be organized for the potential impact of hydrogen-mixed natural gas as fuel on civil/industrial users and other end users. (2) The operation parameters of pipelines at different flow rates, seasons, and hydrogen ratios should be analyzed, and the work condition point variations of different compressors and turbines should be researched. (3) The online/offline chromatographic analysis systems of gas components should be improved with consideration of the factors such as hydrogen content and the stratified flow of hydrogen and methane. (4) The correction of metering equipment should be studied in combination with the CFD simulation and experiment methods. (5) By revealing the leakage and diffusion characteristics of hydrogen-mixed natural gas, the space layout and installation mode of gas leakage detection equipment should be optimized for different leakage scenarios, and a contingency plan should be improved. (6) The adaptability of high-grade steel pipeline to transportation of mixed hydrogen should be analyzed to guarantee the ontological security of pipeline.