Foreign fibers in seed cotton are referred to trashes such as long hair,chemical fibers,Polypropylene(PP)knitted bag pieces,plastic mulching film fragments,which are mixed into cotton during picking,packing,processing and transporting.In China and India,foreign fibers are larger in quantity and harder to detect,which will deteriorate the spinning quality and the market value of cotton in the current cotton grading system.In order to improve the detection accuracy and vision-processing speed,most foreign fibers should be removed at automatic pre-processing stage.