首先介绍了超声冲击金属表面致纳米化的原理、强塑性变形诱导形成纳米晶的机理及纳米晶尺寸和晶粒取向的分析手段，然后结合表面静压力、振幅、单位面积冲击次数等参数变化，总结了超声冲击对金属硬度、粗糙度、残余应力及疲劳性能的影响。超声冲击后，材料表面硬度会大幅提升，表面形貌规则且平整度得到改善。超声冲击诱导产生的纳米晶和残余压应力对提高材料疲劳强度有积极作用。统计认为，超声冲击表面强化对弯曲疲劳试件疲劳性能的提升更大，且试件107周次以上的疲劳极限在(0.50~0.65)σb内。对于处理后产生相变的材料，硬度和强度更高的相甚至能将表层硬度和疲劳极限提高到2倍。最后，综合阐述了超声冲击表面强化与等离子氮化、TiN生物覆膜、常规喷丸及激光喷丸等复合处理方式对材料性能的影响，并提出了基于超声冲击纳米化进行混合表面处理需注意的事项：工艺参数和处理顺序要恰当；考虑环境腐蚀时，要对纳米表面进行二次保护，从而提高材料的综合性能；纯机械方式复合处理要根据技术特点来筛选。

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.