Abstract: This paper introduce the development of flexible drillpipe that used in short radius horizontal well. Because flexible drillpipe strength is low when adopting slot process, so improving drillpipe strength focus on determine slot configuration, selecting materias, manufacturing, heating and welding process to assure stem has enough strength to meet the requirement of horizontal well with 6-12 m curvature radius. Through inspecting, the flexible drillpipe achieve design requirement.