Abstract: A 3D surface modeling, measuring and excavator collision detection system was presented. By using several 2D laser scanning sensors, the system can scan the whole surface in the pneumatic caisson. After registration and segmentation of point cloud, a real 3D scene of the working chamber of the pneumatic caisson can be modeled. With multisensor fusion, the collision detection of excavators and measurement of the pose of the pneumatic caisson can be done. The experiments show that the system has good performance and good stability and can be put into practical use.