Abstract: With the continuous improvement of user needs and the continuous enrichment of spatial data, the same geospatial scope includes different types of spatial data such as terrain, remote sensing images, and 3D models of oblique photogrammetry. 3D WebGIS cannot effectively load different types of spatial data in the same scene. This paper proposes a spatial data loading optimization method for 3D WebGIS to optimize the efficient loading of multiple types of spatial data. First, using the structural features of 3D Tiles with regular enclosing volume shapes and overlapping regions, a fast growth algorithm based on binary tree is proposed to locate and extract the outer boundary of 3D model. Then, there were jagged protrusions on the outer boundary of the roughly extracted polygon. In order to solve the problem, a polygon simplification method based on two neighboring points was proposed to optimize the outer boundary of the polygon to achieve accurate extraction of the outer boundary of the 3D model. Finally, by judging the inclusion of map tile and terrain tile data relationship to achieve selective loading of tile data. Experiments show that when the viewpoint height is below 300 meters, the total load of map tile data can be reduced by about 40%, indicating that the optimization method in this paper can significantly improve the data loading efficiency of the system without affecting the visualization of 3D WebGIS.