Abstract: Based on the measurement of the wall thickness of the tube head/tail end thickened sections,and the regression analysis of the thickness distribution pattern,simulation linear and non-linear mathematical models of the variation rules for the said tube-end thickening phenomenon are set up,and the fit accuracies of them are compared.The result of the comparison shows that with the diameter-reduction rate and the average stretch factor as the key influencing elements for the linear model,the fit accuracy of the wall thickness increase rate is rather high,but that of the thickened section length is rather poor.However,in case of fitting with the nonlinear model,fit accuracies of both the wall thickness and length of the tube-end thickened section are considerably high.This conclusion is worthy using as a theoretic basis for proper control of tube cropping operation.