Abstract: 9Cr-ODS/RAFM steels (oxide dispersion strengthen reduced activation ferritic/martensitic steel) were prepared by powder metallurgy method, and the effects of Ta adding contents on microstructure and mechanical properties of the steel were studied. The results show that the mechanical properties of the steel increased at first and then decreased with the increase of Ta adding content. When Ta adding content was 0.18wt%, the grains were fine and uniform, and a large amount of secondary precipitations of fine TaC particles distributed in grains homogeneously, and the steel exhibited optimal mechanical properties, the tensile strength and the elongation were 632 MPa and 24.2% at room temperature, and were 557 MPa and 23.1% at 300 ℃, respectively.