Abstract: The relationship between main stretch-breaking technology parameters (stretch-breaking settings and ratio) and fiber length irregularity in stretch-breaking sliver was constructed by analyzing the fiber motion in stretch-breaking process. The relationship between input fiber length and stretch-breaking settings affects fiber length irregularity distinct and stretch-breaking ratio has a very small influence to length irregularity. These conclusions reveal inner regulation between main stretch-breaking technology parameters and fiber length irregularity, and it is profoundly instructive to the practice and study of stretch-breaking technique.