Dynamic deformation and failure behavior of U-Nb alloy with different heat treatment (200 oC/2 h, 400 oC /2 h, 600 oC /2 h) were studied. Hat-shape specimens were used in an attempt to induce strain localization in U-Nb alloy. Dynamic load was applied to specimens by use of a Split Hopkinson Press Bar (SHPB) apparatus. The microstructure was examined by optical microscopy and scanning electron microscopy. Results show that the appearance of adiabatic shear bands (ASBs) is relative to the microstructure of material. Different kinds of ASBs are found in 200 oC/2 h and 600 oC/2 h specimens, while specimens (400 oC/2 h) exhibit dimple-like feature, indicating that significant melting takes place during deformation under high strain rate loading condition