The invention relates to a connection-in-series flash furnace. The connection-in-series flash furnace comprises an upper reaction body (5), a lower reaction body (1), and a connecting passage (7) through which the upper reaction body (5) and the lower reaction body (1) are connected, wherein the upper reaction body (5) is positioned at the upper part of the lower reaction body (1), so that a connection-in-series structure is formed; one or more molten pools (2) are arranged at the lower part of the lower reaction body (1); the flash furnace further comprises a lifting flue (3) through which flue gas is exhausted, the lifting flue (3) communicates with the lower reaction body (1) through the molten pools (2), and a slag-off outlet is formed in each of the molten pools (2). The connection-in-series flash furnace disclosed by the invention provides heat and reducing atmosphere for the lower reaction body through the upper reaction body, so that the purpose that mineral fines of metal oxidized ore are rapidly reduced and melted through the lower reaction body is achieved.