Reduced activation ferritic/martensitic(RAFM)steels were highly recommended as the structure materials for tritium plasma and breeding blanket in the next generation of fusion reactors due to its better performance on neutron irradiation resistance than austenitic stainless steels.Yet the higher tritium permeability and subsequently retention of tritium and helium-3 from tritium decay in RAFM steels can lead to a significant loss of tritium and cause hydrogen and helium damages to its mechanic performance.Thus tritium compatibilities for RAFM steels need to be reassessed for their serviceability in a real D-T fusion environment.