The work aims to improve microstructure and surface properties of Ti-6Al-4V. Ti-6Al-4V was treated by ultrasonic deep rolling with different rolling forces (150, 250, 350, 450 N). Microstructure, micro-hardness and residual stress of TC4 alloy after the treatment were examined with micro-hardness tester, X-ray diffractometer, optical microscope (OM) and transmission electron microscope (TEM). With the increase of ultrasonic deep rolling force, thickness of plastic deformation layer increased. However, the increasing tendency slowed down as the force increased. The maximum thickness 338 μm appeared after the 450 N ultrasonic deep rolling treatment. Nanocrystals appeared on the surface of treated samples, and gradually transformed into amorphous state as the force increased. After being treated by 350 N deep rolling, a small amount of twin crystals and massive dislocations formed at the depth of 220 μm from top surface. With the intensification of plastic strain, the twin crystals disappeared, and grains were continuously refined to reach nanometer level eventually. Near-surface hardness increased obviously, and increase amplitude was positively correlated with the force. Compared with the hardness of material matrix (328HV), final micro-hardness after 150 and 450 N treatment, at a distance of 50 μm from the surface, could reach 343 and 381HV, respectively. Residual compressive stress of near-surface, and the maximum residual compressive stress could reach ?875 MPa; and distribution range of compressive stress also increased as the force increased, and depth of affected distance increased from 0.40 mm to 0.58 mm. In addition, the maximum residual compressive stress appeared at the distance of 20~40 μm from the surface. Ultrasonic deep rolling can improve surface microstructure and properties of TC4 alloy, and further influence its structure integrity and service life.