Abstract: Apart from the explicit damage(fiber breaking),fiber-length will be damaged and shortened in top-making by the implicit damage,i.e.fiber hooking and bending.Using a two-end sampling fiber method from a top,two fiber bundle samples,each with one end flush and uniform,are obtained and called sample A & sample B respectively,and from them the length characteristics for analysis of implicit damage of fiber can be got.Implicit damage of fiber can be effectively characterized by the difference rate and the damage percentage determined by the length characteristics.The test results indicate that the fiber hooking rate can be reduced,but there still exist 40% remnants of the hooking fibers,i.e.3%～7% hooking fibers left in tops,and the more sensitive and stable parameters to evaluate the implicit damage are the difference rates calculated from short fiber content(SFC),Hauteur length and Barbe length.