The effect of hafnium addition on the microstructure and tensile properties of aluminum added high-Cr ODS steels Fe-16Cr-1.5W-3Al-0.35Y2O3(16Cr-3Al-1.5W-ODS)were investigated.Results include grain morphology,distribution and composition of nano-oxide particles and tensile properties at room and high temperatures after HIP at 1150℃.Experimental analysis indicated that the addition of Hf refined oxide particles by forming finer Y-Hf-O nanoclusters instead of Y-Al-O nanoparticles and encouraged grain refinement obviously from the results of TEM and EBSD.Besides,the 16Cr-3Al-1.5W-ODS steel containing Hf showed preferable yield strength and ultimate tensile strength compared with two commercial alloys(PM2000 and MA956)as well as the ODS steel without Hf at several test temperatures,indicating the enhancement of tensile properties by the addition of Hf.The improvement of properties is related to the optimization of microstructure closely.