Abstract: Hydrogen injection into natural gas pipeline network transportation changes the thermophysical properties of the original natural gas in the pipeline. The effects of changes in pressure, temperature (283.15-323.15 K) and hydrogen-blended volume ratio (0%-30%) on the thermophysical properties of hydrogen-blended natural gas in the pipeline were calculated and analyzed in this paper for both low-pressure pipeline (0-1.6 MPa) and medium-pressure pipeline (1.6-10 MPa). The Joule-Thomson coefficient, calorific value, Wobbe index, and viscosity of hydrogen-blended natural gas in the pipeline decreased and the compression factor increased when the hydrogen blending volume ratio increased. The calorific value and Wobbe index of hydrogen-blended natural gas increased as the pressure inside the pipeline increased. The viscosity of hydrogen-blended natural gas decreases with increasing temperature, while the compression factor increases with increasing temperature. These results of this paper can provide data reference and guidance for the implementation of hydrogen-blended natural gas projects in the future.