Dynamic testing of Ti-5Mo-5V-2Cr-3Al (TB10) alloy was carried out in hat-shaped specimens by a split Hopkinson pressure bar (SHPB) technique. The microstructure of adiabatic shear band (ASB) in TB10 alloy was investigated by means of OM and TEM. The results show that the transition zone between the shear band and the matrix is composed of grains of 20-50 nm in width with high dislocation density, and the grains are elongated along the shear direction. The center of the shear band consists of a number of recrystallized grains with diameters of 50-100 nm and low dislocation density, exhibiting typical recrystallization characteristics. The average value of temperature rising in the ASB during the adiabatic shearing deformation is about 784 oC. Dynamic recrystallization occurs in ASB and the grain sizes are about 50-100 nm