The surface gradient nanocrystalline structure was fabricated by the surface mechanical attrition treatment (SMAT), and the influence of surface nanocrystallization on the surface microstructure and characteristic of passive film on pure titanium was studied. The anodic oxidation was conducted in 0.5 mol/L H₂SO₄ solution under the potentiostatic mode at 30 V for different durations to investigate the surface characteristic and corrosion resistance of the passive films by optical microscope, X-ray diffraction, Raman spectrometer, X-ray photoelectron spectroscopy, and electrochemical test. The results show that the gradient nanocrystalline structure can increase the film thickness, promote the crystallization, and improve the corrosion resistance of passive film. The influence mechanism of surface nanocrystallization on the corrosion resistance can be explained by the cation-anion-vacancy condensation.