This paper discusses the influence of ultrasonic surface peening on the fatigue property of 7B04 high strength and toughness aluminum alloy. The results showed that a nano-layer of 10-20 μm was formed after ultrasonic surface peening. This nano-layer had a gradient structure with grain size of 10 to 50nm. Further, the ultrasonic surface peening process created residual compressive stress of 200MPa in this nano-layer. This stress caused micro surface cracks to be compressed or closed . Consequently, after ultrasonic surface peening the fatigue life of 7B04 alloy was extended to 5 times.