The spall characteristics of different thicknesses Al7050 alloy treated by laser shock peening (LSP) with different process parameters (Process-1 and Process-2) were investigated to obtain the spall mechanism and spall threshold. The particle velocity of rear free surface and spall crater morphology in 0.33 mm thickness Al7050 induced by LSP with Process-1 were measured and analyzed by a Photonic Doppler Velocimetry (PDV) system and scanning electron microscope (SEM), respectively. Spall sizes, spall thicknesses and spall fracture morphology in 5 mm thickness Al7050 induced by LSP with Process-2 were analyzed by a C-scan ultrasonic nondestructive testing with water immersion, optical microscope (OM) and SEM, respectively. The results indicated that spall strength and LSP strain rate of 0.33 mm thickness Al7050 were calculated by PDV data. Spall crater morphology was also analyzed in detail. Spall sizes of 5 mm thickness Al7050 increased with continued multiple LSP impacts and its spall thicknesses were in range from 343 μm to 364 μm. Spall mechanism was mixture ruptures of ductile behavior with spherical voids and brittle behavior with straight cracks. Continued LSP-5 was the spall threshold of 5 mm thickness Al7050. Compared with as-received material, the micro-hardness of 5 mm thickness Al7050 with continued LSP-5 increased in the surface layer and decreased near rear free surface. The results provided not only some important insights on the spall behavior of aluminum alloy with laser shock but also fundamental research for avoiding the spall in industrial applications.