The invention provides a dry sand preparation device and a dry sand filling system, and belongs to the technical field of goaf filling. The dry sand preparation device comprises a bracket, a base, a first sieve plate, a second sieve plate, a containing groove and a vibrating piece, the bracket is connected with the base through a damping mechanism, and the vibrating piece is mounted on the bracket; the first sieve plate is connected with the bracket, the first sieve plate is provided with a plurality of steps, and the heights of the multiple steps decrease in sequence in the preset direction;the second sieve plate is slantly arranged in the preset direction, and an included angle between the second sieve plate and the horizontal plane is 5-10 degrees; the first sieve plate, the second sieve plate and the containing groove are arranged in sequence along the height direction of the bracket; and a first flow leading part is connected with the end, in the preset direction, of the first sieve plate, and an acute angle is formed between the first flow leading part and the first sieve plate; a second flow leading part is connected with the end, in the preset direction, of the second sieve plate, and an acute angle is formed between the second flow leading part and the second sieve plate; and the containing groove is fixed to the base, and the first flow leading part and the second flow leading part can lead water in gravel to the containing groove. The dry sand preparation device can effectively dewater mortar to get dry sand.