The invention relates to a double-layer steel plate assembled underground barn with prefabricated caulking strips. The flat shape of the underground barn is a round shape. The underground barn comprises multifunctional columns (1), a plurality of prefabricated barn wall plates (2), a barn roof (3), a barn bottom (4) and a plurality of prefabricated caulking strips (5), wherein the barn wall plates (2) are prefabricated steel plate-concrete arc-shaped plates in the flat plane; the peripheries of the barn wall plates (2) are connected with the multifunctional columns (1) and the prefabricated caulking strips (5) to from an integral round tube structure; the multifunctional columns (1) position the barn wall plates; the soil anchoring depth of the multifunctional columns (1) is greater than the depth of the barn bottom (4); and the multifunctional columns (1) are major stress components for bearing soil pressure and grain pressure and resisting the buoyancy force. The double-layer steel plate assembled round underground barn is characterized in that the multifunctional columns (1) are separated into a plurality of sections; a first layer of barn wall plate is arranged at the inner side of the first section at the uppermost layer; a second layer of barn wall plate is arranged at the inner side of the second section; the similar setting mode is used until the lowermost layer of barn wall plate is reached; and a round assembled underground barn structure is formed. The barn wall plates (2) are prefabricated composition plates formed by inner and outer side steel plates (9), anchor nails (10) and middle concrete (11), and steel plates are covered on the periphery for opening sealing.