Abstract: The soil deformation and foundation settlement have always been one of the hotspots in the researches on soil mechanics. The dry density and matrix suction are the two important influence factors for the compressive deformation of unsaturated soils. In order to study the compressive characteristics of the unsaturated sandy cohesive purple soils widely distributed in the Three Gorges Reservoir areas in Southwest China. The GDS unsaturated soil advanced consolidation test system is used to carry out one-dimensional confining compression tests on the unsaturated sandy cohesive purple soils. The influences and rules of change of the initial condition on the compressive characteristics of the purple soils are investigated and a related model is proposed. The research results show that: (1) The e-lgp curve can be decomposed into two parts, and the change of the two sections is different. The increase of dry density will inhibit the soil compression. (2) The e-lgp curve of the purple soils with different dry densities will change with the net vertical direction. When the pressure increases, the void ratio will be concentrated in a certain area. (3) The compression of coefficient suction Q_si is proposed, a model between the the suction and settlement is established, and the foundation settlement is predicted. (4) From the analysis of the influence mechanism, the increase in the suction and density reduces the pore space between soil particles in different ways and to varying degrees. This in turn affects the soil compression. The research results may provide certain reference value for the foundation design and treatment of buildings and roads in the purple land areas.