The cavitation strengthening test of Aluminum lithium Alloy (8090Al–Li) was carried out with different pressure process parameters. The roughness, residual stress, and morphology of the treated samples were studied. A high dislocation density was formed in the cavitation area of the workpiece, which resulted in surfacing hardening. The cavitation effect occurred in the collapse area. It was beneficial for the process to be the right choice for the surface treatment of metal materials. The results confirmed that surface roughness, grain size, micro-strain, erosive effect, and micro-hardness of the alloy were significantly affected by different cavitation peening pressures. In this case, surface roughness increased as the impact pressure increased. Besides, the microcrystalline structure decreased in the cavitation treatment area. The study showed on how the impact of the different cavitation peening pressure could suppress the material surfaces, the compressive residual stress, attained the maximum values of −137 MPa to −162 MPa, which increased from 7.87 to 27.56%, as compared to the original sample. In contrast, the corresponding surface roughness average increased to 3.04 μm. Experimental observation shows that the cavitation collapse boundaries obtained by the proposed sample surface and metallographic images were highly complete and accurate.