The invention discloses a concrete for a spent fuel dry storage container, and a preparation method thereof. The concrete comprises a gelling material, fine aggregates, coarse aggregates, water, composite fibers and a water reducer. The preparation method comprises the following steps: carrying out primary stirring on the coarse aggregates, the fine aggregates and the composite fibers to obtain a first intermediate, adding the gelling material to the first intermediate, and carrying out secondary stirring to obtain a second intermediate; and adding the water reducer and water to the second intermediate, and carrying out tertiary stirring to obtain the concrete for the spent fuel dry storage container. The concrete for the spent fuel dry storage container has very strong resistance to radiation, high temperatures and fire, and meets the demand for the preparation raw materials of the spent fuel dry storage container.