The invention discloses a prefabricated assembly-type underground granary, which comprises a granary bottom, prefabricated granary wall plates, a granary top and multifunctional columns, wherein the granary wall plates are arc-shaped prefabricated plate blocks; connecting devices are arranged on the peripheries of the granary wall plates; the granary wall plates can be connected with the adjacent granary wall plates and the multifunctional columns through the connecting devices; the multifunctional columns are used for locating a granary wall; the depths that the multifunctional columns are anchored into earth are more than the depth of the granary bottom; the multifunctional columns are main stress components for bearing the pressure of the earth and the lateral pressure of grains and resisting buoyant force. The prefabricated assembly-type underground granary is characterized in that the outer sides, the left ends and the right ends of the prefabricated granary wall plates are all clad with steel plates; further, the left ends of the prefabricated granary wall plates are provided with convex-type trapezoidal or semi-elliptical plugs; the right ends of the prefabricated granary wall plates are provided with concave-type trapezoidal or semi-elliptical slots; the multifunctional columns are divided into several sections from tops to bottoms; the inner sides of first sections of the uppermost layer are provided with a first layer of the granary wall plates; the inner sides of second sections are provided with a second layer of the granary wall plates; the granary wall plates are arranged until the bottommost layer of the granary wall plates by using a similar arrangement way, so as to form a round assembly-type underground granary structure.