The authors have proposed an explosive welding process using reflected underwater shock wave to accelerate a thin plate. In this process, an explosive attached on a surface of a steel block is set vertical to the specimen to be welded (a pair of a flyer and a parent plates), and a reflector is placed over the specimen at an angle. The explosive is ignited in the whole set up is submerged in water. When underwater shock wave propagates through the specimen from explosive side to the other side, the shock wave is amplified by the reflector to derive sufficiently high pressure to satisfy the requirements of explosive welding. As the important parameters in this process considered are the inclination of the reflector and other dimensions of the assembly, the experimental results can be changed by varying the dimensional parameters of the assembly.