The invention discloses a large-span rotary supporting type flour mill. The flour mill comprises a hanging bracket and milling roller assemblies connected with the hanging bracket through rotary shafts. The milling roller assemblies rotate through rotary pairs in rotary positions of the rotary shafts. Every two rotary pairs are arranged at the two ends of the corresponding rotary shaft. The rotary shafts can be horizontal shafts or vertical shafts. The flour mill has the advantages that a traditional mode that rotary pairs are arranged in the middles of rotary shafts is changed into the mode that the rotary pairs are arranged at the two ends of the rotary shafts; when milling rollers press materials and bear resistance of the materials, a couple M is generated on each rotary pair, according to the equation that the couple M is equal to P multiplies L, it can be deduced that when M is a constant, pressure P exerted on the rotary pairs is reduced along with increase of L which is the distance between the sliding rotary pairs at the two ends of each rotary shaft, rotation flexibility of the rotary pairs is improved easily, and the service life of the rotary pairs is easily prolonged. Meanwhile, gaps generated when the rotary pairs work for a long time and are abraded can be reduced or eliminated by means of adjustment performed through a rotary device, and vibration occurring during work of the milling roller assemblies is reduced or eliminated.