Abstract: A technique called added-pressure shot peening (APSP),which combined with a pressurizing vessel in the common shot peening equipment,had been applied to shot peen on the surface of 7050 aluminium alloy.X-ray diffraction,optical microscope,transmission electron microscopy and selected area electron diffraction were employed to observe and analyze the surface microstructure as well as microhardness tester for the microhardness of the surface layer.The results show that after treatment the diffraction peak of the alloy surface brodened obvionsly.The thickness of plastic deformation layer increased as the treatment time increase,the surface layer grain was refined into nanometer about 40 nm.The microhardness of nanostructure surface increased by 1.5 times which could be attributed to reduction of grain size and work hardening.