Abstract: Under the background of the transition toward low-carbon energy systems, blending hydrogen into existing natural gas pipelines is regarded as a feasible approach for hydrogen utilization, since the transportation and storage capacities of natural gas pipeline networks can be effectively utilized. To address the technical and safety challenges associated with hydrogen blending in natural gas pipelines, a comprehensive review is conducted on hydrogen blending processes, the adaptability of transmission and distribution systems, the compatibility of end-use gas appliances, as well as leakage, risk, and safety issues. The results indicate that, at low hydrogen blending ratios （≤20%）, existing urban natural gas transmission and distribution systems and most end-use equipment generally exhibit good adaptability and engineering feasibility. However, under higher hydrogen blending ratios, dynamic operating conditions, and complex application scenarios, uncertainties are still observed in material safety, metering accuracy, and combustion stability. Overall, hydrogen blending in natural gas pipeline networks is considered to have promising application prospects, while further research is still required regarding standardization systems, long-term operational mechanisms, and multi-scenario validation.