The primary purpose of an ash silo is to temporarily collect and store fly ash produced by boiler operations, necessitating regular internal environment monitoring. Addressing the challenges of a dusty and visually obscured environment within ash silos, this paper presents a three-dimensional shape reconstruction system utilizing laser scanning technology. The system utilizes a self-developed inverted 3D laser scanning device to capture the original point cloud data of the ash silo. This data is subsequently processed and fed into a 3D reconstruction algorithm to reconstruct the silo′s shape. The system has been tested in a thermal power plant′s ash silo, demonstrating its ability to accurately detect adhesion on the silo′s inner wall and ash deposits at the silo′s bottom.