A combined structural building bin used for storing bulk grains comprises a bin bottom, a bin wall, inter-floor bin bottom plates, a bin top plate, beams, a column, a perpendicular conveying device, a multi-point discharge conveying device, a bin inlet distribution chute and a bin outlet chute. The perpendicular conveying device is arranged at the end of the building bin and used for perpendicularly lifting the grains and conveying the grains to the top of the bin, the multi-point discharge conveying device is fixed at the top of the bin and connected with the bin inlet distribution chute, grains are conveyed into the bin through the bin inlet distribution chute penetrating through the inter-floor bin bottom plates, the bin outlet chute is disposed at the inter-floor bin bottom plates and penetrates through the bin wall, most of grains can automatically flow out of the bin, and other grains are discharged from the bin by a grain elevator and a self-flowing pipeline. The bin wall is formed by coating a layer of steel plate on a concrete inner wall, and the concrete inner wall is connected with the steel plate via steel components so as to form a combined structure. The steel plate is utilized as a formwork of the side wall of the bin wall with the combined structure, thereby saving construction cost of the bin wall, reducing construction difficulty of the bin wall and accelerating integral construction speed. In addition, the combined structural building bin increases rigidity and strength of the bin wall, sufficiently plays tensile property of steel, effectively resists grain lateral pressure, is favorable for higher and larger development, increases application scope, and is waterproof and moisture-proof.