Provided is an underground grain bin including a bin roof, a bin wall and a bin bottom, the bin wall is composed of a plurality of semi-cylinders, the openings of the semi-cylinders toward the inside of the bin, a strengthened column is arranged between every two adjacent semi-cylinders. The underground grain bin in the utility model remains the advantage of good rigidity at the lateral direction of a tower silo, meanwhile, the inner grain storing space of the underground grain bin is enlarged and the grain storing depth thereof is improved.