Bolster of tank wagon

A bolster of a tank wagon includes a draw beam (8), a lower cover plate (7) and a lower middle cover plate (10) of the bolster beam, which are both under the draw beam (8). The lower cover plate (7) of the bolster beam is arranged at the both sides of the lower middle cover plate (10) of the bolster beam, and the lower middle cover plate (10) of the bolster beam is a flat plate structure. The bolster can eliminate the partial space between a lower wing plate of a Z-steel which is at one side of the draw beam (8) and the lower middle cover plate (10) of the bolster beam, and the bending residual stress in the original structure, thus improving the fatigue strength reliability of the structure, solving the problem of assembly with great force in welding the lower middle cover plate (10) and assembly welding the lower cover plate (7) of the bolster beam in the original structure, and improving the strength reserves of the lower middle cover plate (10) of the bolster beam.