Abstract: In allusion to the radial deformation of the pipe towed-back in horizontal directional drilling engineering of Nenjiang crossing project in Daqing-TiJeling Oil Pipeline, an analysis on pipe deformation, design parameters and drilling process is carried out.It is pointed out that less pipe wall thickness designed and unexpected foreign force factors during the drilling process are the main causes.The authors consider that measures for increasing pipe wall thickness, restricting or controlling mud pressure during pipe towing back operation should be taken according to drilling depth and geological condition so as to ensure the safety and reliability in pipeline design.