The invention discloses an automatic cutting type bristle bundle root aligning device. The device comprises a tightening belt, a limiting platform, insertion blocks, a first driving mechanism, a second driving mechanism, and a vibrating table horizontally arranged and having a vibration function, wherein the tightening belt is made of an elastic material for bundling bristles to form a bristle bundle; the limiting platform is located above the vibrating table, the limiting platform is provided with a vertically through limiting groove which is arranged vertically, and the inner circumferentialsurface of the limiting groove is provided with a magnet circling around an inner cavity of the limiting groove; the insertion blocks are made of a ferromagnetic material, the number of the insertionblocks is at least two, and one side of each insertion block is provided with a hook fixed to the insertion block; the first driving mechanism is connected with the limiting platform to drive the limiting platform to rise and fall; and the second driving mechanism is connected with the vibrating table to drive the vibrating table to tilt to one side. The device has a high bristle root aligning rate and a good effect, and can achieve automatic cutting.