Abstract: The surface of Ti3Zr2Sn3Mo25Nb titanium alloy was strengthened by ultrasonic impact. The surface fine grains were characterized by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction and X-ray diffraction. The results show that a strong plastic deformation layer with a depth of about 35 μm was obtained on the surface of titanium alloy after ultrasonic impact. Obvious nanoscale amorphous clusters and dense slip lines could be observed on the surface of titanium alloy. The main reason for the formation of fine grains was dislocation slip and the main direction of dislocation slip was <111>. After ultrasonic impact, the residual compressive stress on the surface of the material was about 250 MPa, the lattice constant decreased slightly, the characteristic peak intensity of β phase increased and the characteristic peak width of α phase increased.