<p>Installing prefabricated vertical drains (PVDs) is a conventional technique to shorten the consolidation process of ground subjected to surcharge preloading. When there is both an unsaturated and a saturated soil layer in the ground, consolidation is a problem worthy of special attention due to the different flow and deformation patterns of each soil layer. An axisymmetric consolidation analytical model for ground that integrates saturated and unsaturated soil layers is developed in this paper, aiming to investigate the complex consolidation characteristic of PVD-improved unsaturated–saturated soil ground under surcharge preloading. The corresponding solutions to the excess pore pressures and consolidation settlement that consider the vertical and horizontal flows of pore fluids within unsaturated–saturated soil ground are proposed via some mathematical methods. After confirming the credibility of the presented solution, the consolidation characteristic of unsaturated–saturated soil ground incorporating PVDs under surcharge preloading is discussed through the calculation of the proposed solution and the visualization of the results. Based on these numerical studies, it is found that when the permeability of pore fluids in the horizontal direction is better than that in the vertical direction, and the pore water permeability in saturated soils is better than that in unsaturated soils, installing PVDs can improve the speed of ground treatment.</p>