Research includes corrosion, dissolution rate, fretting wear and stress corrosion cracking of key nuclear structural materials and weld joints in high temperature pressurized water, mainly focusing on the evolution of microstructure defects, the process of crack incubation, initiation and propagation during long-term service in high temperature pressurized water. Based on the characterization of localized electrochemistry and localized stress on the localized deformed materials, the mechanism of stress corrosion cracking of nuclear materials and control factors affecting materials degradation are explored. Through the optimization of various parameters during manufacture, machinery, transportation and installation of key components and water chemistry, the reliability and the service life of key components are going to be improved.