Abstract: The effect of hydrogen on the irradiation behaviour of oxide dispersion strengthened(ODS) ferritic steel was studied by means of ion bombarding at room temperature and irradiation in HVEM at room temperature and 500℃,respectively. Microstructure of ODS ferritic steel did not change at room temperature after hydrogen-ion bombarding. Observable voids were not formed during in-situ electron irradiation at 500℃ for the specimen bombarded with hydrogen. The electron irradiation experiments at room temperature for the specimens with and without hydrogen-ion bombarding, respectively, were performed. The results indicated that hydrogen played an important role in the motion and collection of point defect.