Uranium-niobium (U-Nb) alloys have excellent corrosion resistance and good mechanical properties. They are good candidates for structural materials and functional materials of nuclear engineering. Fabrication of high quality uranium-niobium alloys using direct vacuum induction melting process is of great significance for efficiency promotion. But unsufficient alloying is the main problem of U-Nb alloy fabricated by direct vacuum induction melting process. The dissolution and diffusion of solid Nb in U melt is the key point of direct vacuum induction melting process of U-Nb alloy. So, in this paper, we investigated the dissolution and diffusion of Nb in U melt using experimental method. The actual dissolution rate of Nb in U melt with different temperature was obtained. The dissolution rate of Nb in U melt v and the melt temperature T have a relation of v=0.3651exp(-21150[K]/T)[m/s]. Scanning electron microscope observation shows sheet structure forms at the U/Nb interface during the dissolution process of Nb in U melt. When electromagnetic stirring is used, the dissolution rate of Nb in U melt increases obviously and the morphology of sheet structure at the U/Nb interface changes.