The invention discloses an external-circulation cement finish grinding system for a vertical mill. The external-circulation cement finish grinding system comprises a belt conveyor, a bucket elevator, a steady current bin, a vertical mill, a dust collector, a fan and a chute, wherein the belt conveyor is used for conveying materials inside, and the chute is used for conveying fine powder finished products outside. The external-circulation cement finish grinding system is characterized in that the bucket elevator, a coarse powder concentrator, the steady current bin and the vertical mill are sequentially connected to form a circulating system; the bucket elevator, the coarse powder concentrator, a refined powder concentrator, the steady current bin and the vertical mill are sequentially connected to form a circulating system; the bucket elevator, the coarse powder concentrator, the refined powder concentrator, the dust collector and the fan are sequentially connected; a powder concentration device is positioned outside the vertical mill and is formed by serially connecting the coarse powder concentrator and the refined powder concentrator; the coarse powder concentrator comprises three paths of air inlet pipelines which are connected in parallel, one path is connected with a heat source, one path is connected with cold air, and one path is connected with a dust collecting air inlet of the vertical mill.