Abstract: Based on SHS technology, rapid underwater welding was investigated. The solder was composed of thermite of CuO+Cu₂O+Al, gasification agent of CaCO₃, alloy agent of FeSi+MnFe and slagging agents of B₂O₃. The weld block was consisted of graphite crucible and rectangular pipe, meanwhile, one end of rectangular pipe was sealed and another one sealed partly to control the heating direction of combustion flame. Tungsten coil was used to ignite KNO₃/Al-Mg ignition materials and the paraffin was used to seal the opening of the weld block. Finally, the feasibility problem of underwater welding based on SHS was solved. It was found that, this technology can be operated easily without power supply to form welded joints after selfcombustion of the solder in weld block. Welded joints with tensile strength of 135 MPa can be obtained under the condition of water depth of 0.5 m, and the emergency repairs of underwater damaged structures can be realized basically.