The utility model discloses an outer hot type rotary kiln for valuable metal comprehensive recovery in the iron-bearing sludge contains driving motor, feeder, discharging device (8), cylinder (3) and transmission supporting mechanism. The burner hearth urceolus of cylinder (3) adopts high temperature casting material lift (2), and high temperature casting material lift (2) outer wall adopts steel sheet casing (24) to consolidate, fills between steel sheet casing (24) and the high temperature casting material lift (2) insulation material layer (1), cylinder (3) one side is equipped with oil gas orifice (5), oil gas bleed pipe (23) looks communications and liaison of oil gas orifice (5) and outer heating system, be equipped with flue gas cooling dust arrester installation on one side of the rotary kiln kiln hood. The utility model discloses have operate steadily, reliably, the valuable metal reduction volatilization is abundant, each primary clustering can be removed and unload, assemble, the convenient maintenance can be satisfied reducing roasting, degree of depth reducing roasting, low-melting-point metal volatilizating roasting, oxidizing roasting, the neutrality of metallurgical iron-bearing sludge and complicated refractory iron ore respectively and calcined.