The activated corrosion product (ACP) assessments of fusion structural materials are essential to designing components and evaluating workers’ radiation exposure. This paper first gives the R&D status of the high-temperature pressurized water corrosion study of reduced activation ferritic/martensitic (RAFM) steels and chromium-zirconium-copper (CuCrZr) alloys, which are the leading candidate materials of fusion reactor in-vessel components such as breeding blanket and divertor, which are utilized in high-temperature and high-pressure water, and the recent progress of corrosion test apparatus simulating the unique environment of a fusion reactor will also be presented.