To address the challenges such as invisibility of the underground environment and the unclear spatial relationships of adjacent pipelines encountered during emergency excavation for buried pipeline leakage repair, a method was proposed to construct the three-dimensional underground space by multi-source data fusion technique. Various data acquired from in-line and external inspection technologies were classified, formatted and integrated firstly. Through spatial coordinate transformation and mileage interpolation algorithms, the data were converted into visualizable spatial features. In the following, an integrated pipeline modeling approach was developed based on centerline coordinates, enabling accurate construction of straight segments and bends. Meanwhile, a library of typical defect and pipeline appurtenance models was established, and an adaptive construction algorithm driven by spatial geometric constraints was proposed to achieve precise positioning and automated pose adjustment of defects and appurtenances. Finally, typical service scenarios such as grassland, desert, and river crossings were incorporated, and a three-dimensional visualization platform was developed, featuring viewpoint control, interactive defect information display, and soil-profile and transparency adjustment. The platform features clear visualization of adjacent pipelines, pipeline-soil spatial relationships, and defect characteristics, providing technique support during emergency leak excavation operations of buried pipelines and pipeline integrity management.