Abstract: In order to perform automatic cladding of large scale shell cover,the positioner and the manipulator are combined based on flexible control techniques.The mathematical model of spherical shell cover for automdlic cladding is established,the relative position and movement between welding torch and workpiece during cladding is discussed.The principle on controlling transition section curves is also given.Computer simulation and experiment results indicate that the automatic cladding method of spherical shell cover is feasible,mathematical model is correct.