An experiment of consolidation and permeability in undisturbed soil was carried out to test and verify the membrane performance of cohesive soil. Undisturbed soil samples were collected from 65 m underground in Tangshan coastal salty area and then size composition, pore characteristics and clay mineral content were tested. The undisturbed soil sample was pressured into ring knife for saturation and consolidation, permeation under stable osmotic pressure was tested with 10 g/L saline, and water flow and Cl^- and Na⁺ concentration of the aqueous solution were regularly monitored. When the permeability experiment came to end, inflow fluid concentration and ion concentration on the surface of the undisturbed soil were tested separately. Results show that Na⁺ and Cl^- concentration almost synchronously increased, and were still rising after reaching the initial infiltration solution concentration. At the end of the experiment, inflow liquid concentration was 1.1 times the initial value of the inflow liquid, and the solution concentration on the surface of the undisturbed soil was 1.5 times the initial value of the infiltration solution. The phenomenon of concentration polarization testifies that the undisturbed soil has certain membrane performance, but cannot play a role in intercepting salt under the experimental conditions.