Abstract: This study investigated the impact of Horizontal Directional Drilling (HDD) underneath an existing high-voltage transmission tower through construction process simulation and displacement response analysis. A three-dimensional finite element model was developed using Midas GTS NX to simulate the complete construction process, including pilot drilling, reaming, and pipeline pullback. The numerical simulation results indicate that the displacements induced by HDD in all directions of the tower remain significantly below the standard limits. These findings demonstrate that the underlying construction does not compromise the structural safety or normal operation of the overhead transmission tower. This case analysis provides a valuable reference for safety assessments in similar engineering projects.