The invention discloses a center shaft for a disc filter. A transmission shaft and a supporting shaft are respectively arranged at two ends of a central supporting cylinder; an outer cylinder composed of a first outer cylinder and a second outer cylinder is arranged at the periphery of the central supporting cylinder; a middle separator is arranged between the first outer cylinder and the second outer cylinder; at least two bracket sleeves are respectively arranged at the periphery of the first outer cylinder and the periphery of the second outer cylinder; runner separators are uniformly distributed between the first outer cylinder or the second outer cylinder and the periphery of the central supporting cylinder; a first blocking plate is arranged between every two runner separators; the rear end of each first blocking plate is perpendicular to the middle separator; a second blocking plate perpendicular to the central supporting cylinder is arranged at the front end of the first blocking plate; and runner holes are formed in the bracket sleeves corresponding to variable cross-section runners. The problem that the center shaft is low in strength and rigidity, large in occupied space and high in energy consumption is solved, sector plates are effectively fixed, and runners with the materials are easy to design, so that the energy consumption is reduced.