Abstract: The underground granary has the advantages of energy conservation, land saving, low temperature, and environment protection. However, resistance of water and moisture from the groundwater has been main concerns for storing grains in underground granary. A plastic-concrete waterproof system using the polypropylene plastic (PP) as the waterproof layer was proposed. In this system, the plastic plate and concrete components were connected with plastic studs. Three plastic-concrete testing models were designed and fabricated based on the different stud spaces for the underground granary. In order to analyze the failure mode, failure mechanism, internal force and deformation of the plastic members under the water pressure, hydraulic loading tests were carried out. The test results showed that: the internal stress and displacement of the plastic plate increased with the increase of water pressure; the larger tensile force appeared at the joint area with the maximum stress unevenly distributed; the stress at mid-span was small with the maximum stress uniformly distributed. The displacement at the mid-span of the plastic plate increased linearly with increase of water pressure, whereas the displacement displacement at the joint changed slightly. On the basis of experimental analysis, the optimal design measures were proposed for the plastic-concrete waterproof system with plastic plate of 10 mm and given connection joints. When the water pressure reached its bearing capacity the failure modes of the plastic-concrete waterproof system were changed with change stud spacing. For the stud space of 200 mm, the joint weld seam was damaged at the water pressure of 180 kPa, which indicated that the overall water pressure bearing capacity of the testing model could be improved by enhancing the weld strength at the joint. For the stud space of 300 mm, the plastic plate was damaged with the water pressure capacity of 80 kPa, which indicated that the overall water pressure bearing capacity of the testing model could be enhanced by increasing the plate thickness. For the stud space of 400 mm, the joint weld seam was destroyed when the water pressure reached 38 kPa, the overall water pressure bearing capacity of the testing model could be enhanced by increasing the strength of the joint weld seam. The research results can provide a reference for waterproof design of the underground granary.