Abstract: The bending formation process is regarded as one of the critical processes as employed by the JCOE production line of the SAWL pipe. The characteristics of deformation of the steel plate during the bending formation process is analyzed in details. As a result,it is identified that after the SAWL pipe is just formed,the neutral layer of the steel plate is inward shifted,and such a change leads to increase of the tube’s circumference,and decrease of the thickness thereof. Also conducted is an analysis of relevant measured data to get related theory verified. Thanks to the above mentioned research activities,the formation parameters of the SAWL pipe,and the width of the steel plate used as raw material will be more properly determined,which means a lot in terms of tube quality improvement and cutting down of material spillage.