Abstract: The distribution of residual stress and full width at half maximum (FWHM) of TC4 titanium alloys after milling and shot peening process was investigated by the X-ray diffraction method. The results show that:the distribution of residual stress and FWHM was co-effected by both the cutting action and plastic deformation action in milling process; the higher the cutting line speed was, the stronger the cutting action was, which made a lower, thinner and compressive residual stress distribution, and moreover, and line speed had a little influence on surface FWHM; the larger cutting depth was, the stronger the deformation action was, which made a complex residual stress distribution and a high FWHM on the surface; shot peening induced a compressive residual stress distribution like a inverted hook, in which the maximum value of the compressive stress was close to the yield strength; the depth of plastic deformation layer of shot peening was larger than that of milling, making the residual stress distribution consistent with each other which was different after milling and before peening.