Abstract: Hydrogen blending in natural gas is one of the efficient and economical ways to transport hydrogen. Compared to natural gas, hydrogen has a wider combustion limit, lower ignition energy, and higher risk of leakage and diffusion. In this paper, the leakage and diffusion models of hydrogen-blended natural gas （HBNG） in gas well and atmospheric space are established, and the process of gas leakage and diffusion is analyzed from the aspects of concentration distribution, leakage velocity, velocity flow line and gas cloud volume. The leakage diffusion of hydrogen-blended natural gas is compared from the aspects of pipeline operating pressure, hydrogen blending ratio and leakage point location. It is found that increasing pipeline operating pressure and hydrogen blending ratio will increase the diffusion rate of HBNG. The location of the leakage point has little influence on the leakage diffusion, and the leakage jet mixing of the two leakage points will accelerate the growth of gas concentration, and it is easier to form a large volume of combustible gas cloud.