Sandstone formations are widely distributed in our country, and their hydraulic characteristics affect the engineering stability. Dry density is an important factor affecting soil-water characteristic curve, but the mechanism of its influence on soil-water characteristic curve of sandstone remains unclear. In order to explore the soil-water characteristic curves and microscopic characteristics of sandstones with different dry densities, soil-water characteristic tests of sandstones with different dry densities were carried out by using pressure plate instrument, and a model of sandstones soil-water characteristic curve considering dry densities was proposed. Meanwhile, microscopic characteristics of sandstones with different dry densities were analyzed based on scanning electron microscope and mercury injection test, and the microscopic mechanism of the influence of dry densities on sandstones soil-water characteristic curves was revealed. The results show that the higher the dry density, the stronger the water holding capacity of sandstone. Dry density has an effect on both intake value and residual saturation of sandstone, and the intake value of sandstone increases approximately linearly with the increase of dry density. The pore diameter distribution of sandstones with different dry density is unimodal, and the peak pore radius of sandstones decreases gradually with the increase of dry density. Sandstones with higher dry density have tight grain arrangement and small pore radius, which are mainly medium and small pores, while sandstones with lower dry density have loose grain arrangement and large pore radius, including pores of different sizes. The research can provide some reference for the engineering safety of unsaturated sandstone.