Hydrogen energy is recognized as the most promising energy carrier of the future due to its clean and efficient characteristics. As the cleanest fossil energy resource, natural gas development is currently in its booming period. There are a huge number of pipeline network built and planned around the world, so it has been a hotspot of domestic and overseas research and testing in recent years to blend hydrogen into existing natural gas pipeline network for storage, transportation and utilization. In this paper, after exploring the research status of NCNG, typical project cases, technical issues and application advantages at home and abroad, we have reached the conclusion that HCNG is still the best way for efficient storage & transportation and expanding the unitization of hydrogen energy despite the existing problems. Related technical study and issue tackling shall be pushed forward proactively.