Abstract: In order to discuss the effect of fiber length distribution on yarn properties,researchers prefer fiber length density function,for some mathematical methods can be adopted conveniently and the density function is the best way to describe the entire length distribution.Based on Premier test data,this approach uses kernel function method to estimate the density function of cotton fiber length.The goodness of fit is verified by comparing the calculated and tested value of the SFC of 12.7 and 16 mm,and the analysis results in the conclusion that a power-type kernel function and a normal kernel function are superior.The estimation lays a foundation for the study of cotton fiber length and the prediction of yarn quality based on the data from the equipments like HVI.