Abstract: The length distribution of sliver fiber under conditions of different feed plate gauge was tested by USTER AFIS and fiber length distribution in taker-in droppings and card strips was tested by cotton fiber length analyzer.The results prove that the feed plate gauge remarkably affects fiber length distribution of card sliver.In general,the longer the gauge is,the less is the damage to the fiber.The reason is that a longer gauge will decrease the cotton length for carding.It is proposed that the fiber damage will be judged by both fiber length distributions in droppings and in card sliver.It may be one-sided to judge the damage only by short fiber content in card sliver.