Abstract: The welded joints of commercial pure titanium were treated by surface mechanical attrition treatment.The mean grain sizes of the surface layer were measured by X-ray diffraction and transmission electron microscope.The results show that the mean grain sizes of the surface layer in the weld and heat affected zone(HAZ) reach the nanometer scale,and the depth of nanocrystallization is about 30~40 μm.The microhardness of the treated weld and HAZ incrensed obviously.The corrosion tests reveal that the corrosion resistance of the treated weld and HAZ was improved in HCl solution.