Abstract: Machine harvesting increases the foreign matter content of seed cotton.  Excessive cleaning causes fiber damage and economic loss.  Most trading companies in the Xinjiang Uygur Autonomous Region, China have indicated reluctance to use machine-harvested cotton.  The first objective was to determine how the fiber quality was affected by the ginning and lint cleaning and how the fiber damage during levels of lint cleaning changed. The second objective was to determine the optimum number of lint cleaners for machine-harvested cotton based on fiber damage.  Cotton samples were collected from 13 fields and processed in seven ginneries between 2013 and 2015.  The results indicated that ginning and lint cleaning didn’t have significant effect on fiber strength and significantly affected both fiber length and short fiber index.  Fiber length was reduced by more than 1.00 mm from six of 13 fields after lint cleaning, then the damage rate on short fiber index from 11 of 13 fields was more than 20%.  The third lint cleaning caused great fiber damage, reducing fiber length by 0.35 mm and increasing short fiber index by 0.65%.  So, the lint should be cleaned by one lint cleaner in the Xinjiang, however, the stage of lint cleaning was sometimes omitted when the foreign matter content of lint was little.

Key words: Xinjiang ,  machine-harvested cotton ,  lint cleaning ,  foreign matter