Abstract: Using aQura analysis instrument,the changing rule of the quantity and diameter of neps from raw material up to the finishing drawing during processing combed yarns with rotor spinner was analyzed.It was found that the number of beaters in the process of opening and cleaning is the main factor that affects neps producing on finished yarns,and the quadratic correlation between the number of beaters and opening and cleaning is also determined.This paper discusses the calculation of rotor combed cotton yarn neps and the ability of rotor spinning to eliminate neps of yarns with different linear density.The regression relation between the neps on combed sliver and the neps of different grades on rotor spun yarn was obtained by using the function polyfit in MatLab mathematical software to fit the least square curve.The research work is considered to be of reference value in quality control and process optimization.