Due to the increasing energy demands and accelerated environmental issues, there is an urgent need to improve the thermal efficiency of coal-fired power plants.To achieve this goal, the advanced ultra-supercritial(700℃-750℃, 37.5M pa) power plant are under development.However, the increased operating parameters need more stringent requirements on the candidate materials.Conventional ferrite and austenitic steels can hardly meet the requirements, thus are supposed to be replaced by Ni-based superalloy, such as Inconel 740h and Haynes 282.High temperature mechanical properties and high temperature oxidation resistance of the two candidate materials have been reported, but few studies have been conducted on the stress corrosion cracking of the candidate materials, which may be one of the main forms of failure.The present work investigated the effect of chloride and DO on stress corrosion cracking of Inconel 740h and Haynes 282 in room temperature water using SSRT.The results indicated that both materials show good resistance to SCC at 1ppb CI-and 10ppb DO.But, chloride and DO can individually increase the susceptibility of SCC of the two candidate materials and the synergistic effect of chloride and DO is huge.Therefore, the chloride and DO content should be reduced to as low as possible in the water loop to minimize failures of materials in the advanced ultra-supercritial power plant.