The utility model relates to an expansion pipe technical field that the oil drilling was used, in particular to expansion pipe seals double thread. The internal thread of the device's expansion pipe Iincludes first section internal thread and second section internal thread, is equipped with seal section I between first section internal thread and the second section internal thread, and second section internal thread left end is equipped with the draw -in groove, the external screw thread of expansion pipe II include first section external screw thread closing with the interior thread to matchof first section and with the second section in the second section external screw thread that closes of thread to match. The utility model discloses an adding the rubber circle between two sections screw threads, also guaranteeing to seal under high -pressure condition, screw thread department pipe wall has been done the thickening and has been handled, prevents pipe wall breach that appears thinexcessively after the inflation, reinforcing construction security, simple structure, easily processing.