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With many types of salt structures developed in the Lower Cretaceous Aptian Formation, the passive continental marginal basins in the middle segment of the south Atlantic are hot areas of deep-water petroleum exploration. Based on analysis of differential deformations of salt structures, the influences of the inclination of subsalt slope, subsalt topographic reliefs and basement uplifting on the formation of salt structures were analyzed by physical modeling in this work. The experimental results show that the subsalt slopes in the middle West Africa basins are steeper, so the salt rock is likely to rapidly flow towards the ocean to form larger and fewer salt diapirs. In the Santos and Campos basins, the basement uplifts outside the basins are far from the provenances, which is conducive to the intrusion and accumulation of salt rock on the top of the basement uplifts. In contrast, in the middle West Africa, the basement uplifts are close to the basin margin, the residual salt layers above them are thin, and small triangular salt structures develop on both sides of the uplifts. Moreover, the uplifting of the African plate is also conducive to the full development of salt diapirs in the middle West Africa and results in large-scale thrust faults and folds in the front compressional zone.