The hardness and grain refinement mechanism of V-5Cr-5Ti alloy by equal channel angular pressing (ECAP) and annealing treatment were studied. ECAP was tested using pressing die using universal material testing machine. The annealing was done in vacuum heat treatment furnace. The hardness was tested using Vickers hardness tester. The phase structure was identified using X-ray diffraction (XRD). The microstructure was observed using optical microscope (OM). The results indicated that the grain size of V-5Cr-5Ti alloy can be refined from ~100μm to ~30μm after ECAP two times and annealed above 950℃. Different from the traditional grain refinement mechanism of B.C.C alloy, the grains of V-5Cr-5Ti alloy are rotated on itself at ECAP process, and a lot of shearing glide bands are formed in coarse grains. With the annealing temperature increasing, fine grains are formed gradually at shearing glide bands and the initial grain boundaries are still clear. Finally, the fine grains are formed completely above 950℃, and the initial grain boundaries become blurred gradually.