Abstract: It is of great value to intuitively describe the distribution of shielding failure risk of extra/ultra high voltage transmission lines, and to demonstrate the interaction relationship between complex factors such as line structure, terrain, lightning activity, etc. Relevant research needs to be deepened urgently. This article conducts research on the visualization method of multi-source data fusion for shielding failure risk assessment. Based on the analysis of multi-source data features such as transmission channel point cloud data, EGM model parameters, and shielding failure flashover rate, and referring to the cognition process of "generating intelligence through data", a data fusion 3D visualization framework and key technologies are proposed. This method adopts a hierarchical data structure of "span-wire-section-calculation point-exposed arc", correlates and integrates data with different dimension requirement to express according to a hierarchical structure, and carries out the visualization of shielding failure risk mechanism with exposed arc as the carrier in the point cloud space of the transmission corridor, realize the comprehensive 3D display of multi-source information such as shielding failure flashover rate, shielding mechanism, lightning current peak, etc. By supporting responding to limited conditions, the application of shielding fault analysis is implemented. The application results of one 500 kV line span case show that the fusion visualization can exert the advantages of 3D views including multi-scale and multi-perspective. By complementing the information of exposed arcs and point cloud data, the shielding effect that the conductor receives from the lightning shield conductor and the ground can be revealed from a mechanistic perspective, improving the comprehensiveness and intuitiveness of data visualization.