The invention relates to a box board steel structure fabricated building system, and belongs to the field of fabricated buildings. The problems that an existing steel structure house is poor in flatness, not resistant to fire and poor in sound insulation effect, beams and columns are exposed, the house building space is influenced, and the seismic performance is poor are solved. The building system adopts the mode that the two sides of steel structures are assembled with thermal insulation fireproof materials, fireproof decorative sheets, interior decoration systems and floor structures or themode that an outer curtain wall system forms a fireproof partition wall, a floor slab and an integrated outer wall of a building, the steel structures are composed of steel plates, T-shaped girders and L-shaped girders, and the T-shaped girders and the L-shaped girders are vertically welded to the steel plates in a staggered mode. A pipeline system of the box board steel structure fabricated building system is arranged in the ground empty space and the keel space of the partition wall, a pipeline of a water feeding system is arranged in the keel space of the fireproof partition wall and the ground empty space, and the pipelines are completely separated from pipelines of the structure main body. The box board steel structure fabricated building system achieves the excellent material mechanical properties and the advantage of facilitating industrial production, and has the advantages of being convenient to machine and construct, high in efficiency and precision and the like.