This study addresses the issue of insufficient accuracy in Ground Penetrating Radar (GPR) for urban underground pipeline census and safe operation and maintenance by introducing the GprMax forward numerical simulation software to systematically quantify the influence mechanisms of key parameters, including pipeline burial depth, diameter, material, and filling medium on electromagnetic wave field responses. The research reveals that the relative permittivity of subsurface media serves as the core controlling factor determining radar wave field energy attenuation and reflection intensity. Building upon this finding, and targeting the current challenge of accurately characterizing the three-dimensional spatial structure of complex underground pipelines, this study proposes a joint analysis method integrating "three-dimensional slice reconstruction+structured feature extraction along slice B-scan+three-dimensional attribute volume fusion." This method effectively overcomes the limitations of traditional two-dimensional profiles that can only display images or single attributes, enabling precise revelation of pipeline spatial orientation in the thickness extension direction. It provides a solid theoretical basis for optimizing on site detection schemes and data interpretation, while also establishing a comprehensive data foundation for constructing high-precision three-dimensional visual geological models.