Abstract: Fiber-length will be damaged and shortened in top-making due to fiber breaking, namely the explicit damage. A one-end uniform staple sample (sample C) is prepared by aligning twice through pulling_out fibers from both ends of the fiber bundle respectively, and length parameters of fiber-length damage can be obtained through analyzing sample C. The difference rate and the damage percentage calculated from the length parameters can be used to characterize fiber-length explicit damage effectively and accurately. The test results verify that the explicit damage takes place in all processing processes of the top with an average damage percentage of 8.763%, and the length shortening of the damaged fiber may reach up to 86% of the original one. Meanwhile, the sensitive and stable parameters to evaluate the damages should be expressed by the average weighted length of the short fiber content (SFC) length and the number of fibers.