In order to study welding technology with higher heat input for super thick plates,the double-wire,three-wire and fourwire submerged arc welding experiments were carried out for steel plates of E36 W with thickness of 50 mm and 80 mm. The welded joints were tested by tensile and impact test. The experimental result shows that the mechanical properties of the joint after multi-wire submerged arc welding meet the requirements of marine engineering steels. The relative low impact toughness was exhibited in the weld metal. As the number of wires increases,the content of pre-eutectoid ferrite in the weld increases,and the grain size increases,which resulting in the decreasing of impact toughness. In the same welding process,the content of pre-eutectoid ferrite in 80 mm thick plate welds is more,and the grain size is larger,which resulting in the impact toughness decreasing.