An investigation has been carried out on the adiabatic shear band (ASB) in a Ti-3Al-5Mo-4.5V (TC16) alloy deformed at high strain rate by a split Hopkinson pressure bar (SHPB). ASB in TC16 alloy is a "white" band with a width of about 13 mu m. Microhardness of the ASB is larger than that of the matrix. The elongated cell structures of width about 0.2-0.5 mu m with thick dislocation exist in the boundary of the shear band. Results suggest that the fine equiaxed grains with alpha-phase and alpha ''-phase coexist in the shear band. The "white" band is a transformation band. Calculation of the adiabatic temperature rise indicates that the maximum temperature within ASB is about 1,069 K that is above the phase transformation temperature. Finally, formation of an ASB in the TC16 alloy and its microstructure evolution are described.