The invention relates to a steel-concrete composite beam structure suitable for a heavy haul railway. A steel main beam adopts double pieces of I-shaped steel, studs are welded to the upper surface ofthe I-shaped steel, and the steel main beam and a bridge deck are connected into a whole. A beam body adopts variable-section design, the height of the beam body at the end can be adjusted accordingto the needs, the variable-section position adopts arc transition, stiffening ribs are arranged at the arc transition section of the steel main beam and a top beam point, and a middle lateral combination or an end lateral combination is arranged between the double pieces of I-shaped steel. The main beam spaces of the double pieces of I-shaped steel are open, and thus examining and maintenance arefacilitated; the beam body is simple in structure, can be manufactured in a factory according to the needs, then transported to a bridge site to be erected, and can also be spliced on the bridge siteto be subjected to concrete casting in situ; and through variable-section design, the limiting requirements of a bridge pier for the structural height are met, and through the lateral combination connecting mode, it is ensured that the beam body structure has enough transverse stiffness.