The principle of ultrasonic impact nanocrystallization (UIN), the generation mechanism of nano-crystal induced by severe plastic deformation, and the methods to analyze size & grain orientation of nano-crystal were introduced firstly. Secondly, the influences of ultrasonic impacts on the hardness, roughness, residual stress and the fatigue properties were summarized according to the variation of static load, amplitude, impact numbers per unit area and other parameters. After the ultrasonic impacts, the surface hardness increased substantially, the surface topography was inerratic and the flatness was better. Normally, nano-crystal and residual stress generated by ultrasonic impact had a positive role on improvement of material fatigue strength. According to statistical data, after surface strengthening by ultrasonic impact, the fatigue performance of bending fatigue specimens was improved even more and the fatigue limit of treated specimens for more than 107 cycles was within (0.50~0.65)σb. For materials with phase change after treatment, surface hardness and the fatigue limit could be improved to be twice of the original due to the phase with higher hardness and intensity. Finally, the effects of the hybrid surface treatments on the properties of materials were comprehensively expounded, such as UIN+plasma nitriding, UIN+TiN film coating, and UIN+short peening or laser peening. Three suggestions about ultrasonic impact based hybrid treatment are put forward: 1) Processing parameters and sequence should be appropriate; 2) To improve the overall performance of materials in corrosion environment, secondary protection should be given on the nano-grained surface; 3) Double reinforcement by pure mechanical methods should be chosen according to characteristics.