The invention relates to a double-layer assembly type underground grain silo. The double-layer assembly type underground grain silo comprises a silo bottom, an outer silo wall, an inner silo wall, a silo top and multifunctional columns, wherein the inner silo wall and the outer silo wall are respectively formed by splicing a plurality of prefabricated plate blocks, a connecting device is arranged around the prefabricated plate blocks, and each prefabricated plate block is connected with the adjacent prefabricated plate block and the multifunctional columns through the connecting device; the multifunctional columns are used for positioning the silo wall, the anchoring depth into the soil is deeper than the depth of the silo bottom plate, and the multifunctional columns are main stress members for bearing the soil pressure and grain pressure and resisting buoyancy. The double-layer assembly type underground grain silo is characterized in that the outer silo wall and the inner silo wall are connected by the multifunctional columns as a whole, so as to form a stereo space structure, thus bearing the soil pressure, grain side pressure and buoyancy; an air ventilation and water leakage check channel is arranged in a gap which is defined by the outer silo wall, the inner silo wall and the multifunctional columns; each multifunctional column is separated into a plurality of sections from top to bottom, a first silo wall plate is arranged on the inner side of the first section at the uppermost layer, a second silo wall plate is arranged on the inner side of the second section, and the silo wall plate of the bottommost layer is arranged in a similar way, so as to form the double-layer assembly type underground grain silo.