Dynamic shearing experiment has been done for TC6 titanium alloy by using a split Hopkinson bar process. The fine structure of adiabatic shear band of TC6 alloy under different evolvement stages has been studied by optical microscope (OP), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that the formation of adiabatic shear band of material goes through the three processes of initiation, expansion and full evolvement, for which the fine structure is quite different. The extent of plastic deformation increases gradually from the initiation stage to the full evolvement stage, during which the dislocations play a very important role.