Abstract: According to the demand of high efficient bead welding technology for the manufacturing of heavy vessel in nuclear power and petrochemical industry,the process and microstructures of twin-strip submerge arc bead welding were researched based on the development of submerged arc welding head with one molten pool. The results show that,strip feeding rate,welding speed and are voltage can affect the weld width and height. The weld width and height increase as strip feeding rate being increased,while they decrease with the welding speed being increased. In general,the rate of dilution with twin-strip bead welding is lower than 10%,and it has the advantages of high efficiency and low dilution. The deposited layer is well fused with the matrix,and no defect was found. The microstructure consists of ferrite and austenite.