The invention discloses a bag filter-type manganese processing rotary kiln system with a highly demountable induced draft fan. The bag filter-type manganese processing rotary kiln system adopts the structure that an air-lock valve used for feeding is arranged at the high end of a rotary kiln; the high end of the rotary kiln is connected with a cyclone dust extractor, an induced draft fan and a bag-type dust remover via a fin section and air pipes; fins are arranged in the fin section; a hood cylinder is arranged outside the fin section; a sleeve-type air heat exchanger is arranged outside an air pipe; the hood cylinder is communicated with a lower pumping hole in the air heat exchanger, and then divided into two paths for supplying preheated air; and the blades of the impeller of the induced draft fan are arranged in a radiation shaped and are in radial and central symmetry with respect to an impeller shaft, so that dust can be cleaned promptly via centrifugal force, and safety accidents can be avoided. The bag filter-type manganese processing rotary kiln system not only is high in heat efficiency, but also has the advantages that the demounting technology of the induced draft fan is greatly improved; pressure of a nut-like component on a shaft shoulder end surface of a screw can be eliminated simply during demounting, the problem that a threaded assembly of the induced draft fan is automatically screwed continuously under the action of a load to be difficult to demount can be solved effectively; the suitability for convenient demounting of a large-scale induced draft fan after thread screwing is high; and the effect is remarkable.