Design efforts have been made to develop the assembly procedure of the Vacuum Vessel (W) and the Blanket (BL) Back Plate (BP) of the International Thermonuclear Experimental Reactor (ITER). This procedure must mitigate accumulation of welding distortion of the thick wall structure, handle and assemble massive structures such as the BP within narrow space and certain accuracy, and minimize assembly schedule. As a result, candidate procedures have been developed which rely on symmetric welding, limited rotation and reasonable schedule. Based on these procedures, the detail design of jigs and tools has been started.