The present invention relates to a drafting system for a ring frame, which comprises front rollers, front belt rollers, middle rollers and middle belt rollers, wherein a front jaw is formed between the front belt roller and the front roller; a middle jaw is formed between the middle belt roller and the middle roller; a negative pressure tube is formed between the front roller and the middle roller; a recess is formed in the middle of an upper surface of the negative pressure tube; the upper surface of the negative pressure tube is provided with a front gathering mouth and a rear gathering mouth; a tension device is disposed below the middle roller and the negative pressure tube; a flexible ring made of poromeric materials winds around the middle roller, the upper surface of the negative pressure tube and the tension device and completely covers openings of the front gathering mouth and the rear gathering mouth; an upper pin is formed between the front belt roller and the middle belt roller, above a connecting line between the front jaw and the middle jaw; a cambered boss is formed on a lower surface of the upper pin; and a downward extending end portion of the cambered boss abuts against the flexible ring at the recess on the upper surface of the negative pressure tube. The drafting system provided by the present invention is applicable to ring frames and mainly used for the orderly and uniformly arrangement of fibers.