9Cr2WVTa steel is one kind of reduced activation ferritic/martensitic (RAFM) steels which exhibit lower thermal expansion coefficient, higher thermal conductivity and less irradiation swelling compared with austenitic steel. It has been considered as the candidate structural material for the accelerator driven subcritical system (ADS). Due to the narrow heat affected zone and large depth to width ratio, electron beam (EB) welding is expected as a potential technique to connect components of ADS. However, few previous studies have focused on the weldability of 9Cr2WVTa steel by EB welding. In this work, EB welding was applied to join the 9Cr2WVTa steel and tempering was used to modify the microstructure and mechanical properties of the weld joint. Microstructure analysis shows that the weld metal consists of coarse lath martensite and d-ferrite. After high temperature tempering, large amounts of M₂₃C₆ type carbides precipitate in the matrix. Tempering lowers the hardness of the weld metal. Tensile tests show that the strength of the weld joint decreases, but the total elongation increases after tempering. It was found that the accurate impact energy of the weld metal was not able to be measured with standard Charpy impact specimen due to the crack deviation from the weld metal to the base metal. In order to estimate the impact property of the weld metal accurately, Charpy V-notch specimens with side-grooves were used. The result shows that tempering induces a significant improvement of the impact energy to the weld metal compared with the as-welded condition. Furthermore, the weld metal demonstrates better impact property than the base metal, which results from the existence of low fraction of d-ferrite in the weld metal.