Abstract: During the slight-stretch reducing process of hot-rolled seamless steel pipes，normally，it is impossible to get the inner hexagonal defect developed. Nevertheless，in case of producing heavy-wall tubes，frequently， the slight-stretch reducing operation causes the quality defect of transversal uneven wall thickness. With employment of the ANSYS/LS-DYNA finite element（FE）software，the stress and strain statuses of different stands are dynamically simulated，which leads to identifying the fact that even in case of the pipe being slight-stretch reduced，there still exists circumferential wall thickness difference. Given that the total reduction ratio remains unchanged， decreasing the reduction ratio of the individual stand will eliminate the defect of circumferential wall thickness difference.