This article is devoted to the influence of short cotton fibers and trash on the yarn quality parameters, as well as the yield of yarn and waste of cotton fiber. Carding process at a spinning mill is the last step of removing trash and defects such as neps, peel, seed count neps. Flaws found in the card sliver directly affect the number of defects in the yarn. These defects can not be detected by weight testing and roving sliver. In order to determine short fibers in the card sliver modern fiber measuring instrument USTER AFIS PRO-2 is used. As an object three different lots of cotton fiber of sort 1 in 4 types of selection C-6524 were taken from three different cotton cleaning factories. Studies have shown that removal of neps, short fibers and trash are not dependent on each other. As well as analysis of the results showed that the yarn produced from cotton fibers in cotton cleaning factory-1 meets 5% level according to international standard USTER tester. In this factory cotton fiber have been reported with short fiber content of about 5.6%, and the number of neps 227 units per gram of fiber. Second and Third cotton factories' fibers comprising a short fiber content of 8.7% and 10.3%, and the number of neps are 269 and 280 units respectively. Studies showed that the content amount of short fibers is not changed, and in the process of carding even increases so that it requires careful research.