The microstructure evolution of titanium alloy was decided with deformation rate in cold-deformation process, and substructure significantly influences phase transformation behavior in isothermal aging treatment. The microstructure evolution in cold-deformation and aging behavior of the TB8 alloy was investigated by X-ray diffraction (XRD), Vickers hardness (HV), field emission scanning electron microscope (FESEM) and differential scanning calorimeter (DSC). The high value of FWHM resulted from the combination of the grain distortion and dislocations, and the enhancement of the distortion and dislocations was indicated by increasing of HV value. The phase transformations of this study have reversed the effect of cold-deformation on transformation behavior of α phase precipitation in the β matrix. It suggested that there existed a possibility of a special behavior in the aging transformation of cold-deformation titanium alloy.