Abstract: Hydrogen is an important clean energy carrier that contributes to the carbon neutrality by reducing the dependence on fossil fuels. As its role in the global energy system continues to expand, the demand for the hydrogen blended natural gas transportation is steadily rising, which bring a new challenge of the uniform mixing for the safe and efficient long-distance transmission. In this study, the mixing performance of the Sulzer SMV static mixer for hydrogen blending in natural gas pipelines is investigated numerically. Using the large eddy simulation method, and a detailed parametric analysis of geometric factors including element orientation, aspect ratio, twist angle, and spacing are conducted. The results indicate that the SMV mixer markedly enhances the mixing of hydrogen and methane. Increasing the number of mixing elements from one to six improves the mixing homogeneity but causes a 4.5 times increase in the pressure drop. The flow field visualization and vortex evolution analyses demonstrate that vortex generation plays a dominant role in fluid disturbance and mixing enhancement, with Dean vortices being particularly effective in promoting hydrogen and methane blending. This study provides valuable guidance for the design and optimization of static mixing devices, thereby advancing the hydrogen utilization and improving energy efficiency in sustainable energy systems.