Abstract: In order to study the diffusion characteristics of pure hydrogen/hydrogen-doped natural gas in the soil environment, a three-dimensional leakage model of the buried pure hydrogen/hydrogen-doped natural gas pipeline was established by Fluent software. On this basis, the effects of the characteristics of the leakage port, buried depth of the pipeline, soil condition, pipeline pressure and hydrogen blending ratio on the leakage of buried pure hydrogen/hydrogen-doped natural gas pipeline were analyzed. The results show that: the leaked hydrogen diffuses at a relatively slow rate in the soil environment but gathers near the leakage port. The larger the leakage aperture, the larger the aspect ratio of the leakage port, and the greater the hydrogen leakage risk. Besides, the location of the leakage port will have a main effect on the distribution of leaked hydrogen. For the large hydrogen pipeline, the hydrogen concentration should be monitored around the pipelines to avoid hydrogen leakage accidents. The shallower the pipeline is buried, the more the leaked hydrogen and the greater the risk. As the hydrogen leaks and diffuses faster in soil with large porosity and large particle size, different hydrogen transportation monitoring schemes should be designed for different soil conditions. In the process of hydrogen-doped natural gas transportation, the time required for the mixed gas at the same monitoring point to reach the lower explosive limit becomes shorter with the increase of the hydrogen blending ratio, which increases the risk of hydrogen leakage gradually. Generally, the research results can provide theoretical reference for the safe and stable operation of pure hydrogen/hydrogen-doped pipelines in the future.