Aiming at the problem of automatic processing of ship hull plate, a kind of automatic processing system of water fire bending plate was designed, and the key technology of the system was studied. The 5axis gantrylinked design was used in this system, so as to meet the processing requirements of large curvature ship hull plate. Besides, based on the 3D laser measurement technology, the coordinate system transformation method, trajectory planning and 5axis control quantity calculation method were researched to realize the positioning and machining of the hull plate. The experimental resulst show that this system can replace the workers for processing work of the hull plate, which has certain practical application value.