Abstract: The Al-Cu-Mg alloy sample was treated by composite shot peening. The effects of composite shot peening on the surface morphology and mechanical properties of Al-Cu-Mg alloy were analyzed by observing the surface morphology of sample after shot peening and measuring the surface roughness, residual stress, half maximum width of diffraction peak and microhardness of sample. The results show that the surface roughness of Al-Cu-Mg alloy sample increases little from 0. 7 mm to 2. 97 mm after composite shot peening, the surface of sample is fine and uniform, and has high integrity and good surface quality. The deep residual pressure stress field is introduced, the maximum residual pressure stress is 306 MPa, and the overall distribution of the stress field is uniform, which can play a good strengthening effect. The half peak width of surface diffraction increases to 0. 275°. The surface microhardness increases to 180. 8 HV, which is 50% higher than matrix of 120 HV.