Dissimilar Metal Welds have been widely used at safe-related pressure vessels and piping in Nuclear Power Plants. Some industry codes have been developed for nuclear power plants, such as ASME BPVC volume III & XI, Germany KTA 3201.3 and 3201.4 code and Russia code of light water nuclear power plants. The difference of those codes and some industry feed backs and some experiment results have been briefly introduced and discussed. Furthermore, the inspection qualification or performance demonstration, one of new requirements of some codes, especially for pre-service and inservice inspection of nuclear power plants, really promote continual improvements of DMWs UT both on detection rate and sizing accuracy. Additional, these works really benefit the revision of EJ/T 1039-1996, Non-destructive testing for mechanical components in nuclear island of nuclear power plants, as china building more and more nuclear power plants.