Deformation of pipe during rotary-draw bending is studied theoretically and experimentally.The effect of main technical parameters on the change of wall thickness and section flattening are analyzed with plastic FEM software,meanwhile the variety of wall thickness and section flattening in different location of pipe are studied experimentally.The result shows: the smaller R/D,the bigger the wall thickness change.The effect of t/D on wall thickness change is weak.The dimension and position of the mandrel have a big impact on wall thickness and section flattening.The conclusion is helpful to improve the quality of the rotary-draw bending of pipe.