A duodenal internal covering membrane can be made of a degradable shape memory biocompatible material and is a degradable medical instrument built in a digestive tract. After the internal covering membrane is implanted into a duodenum, chyme can be split from bile and pancreatic juice, so stomach exudates are prevented from being directly digested, absorbed, and metabolized in the duodenum, and the histocompatibility is good； after being implanted into a human body, the duodenal internal covering membrane is steady, is not easy to slide off to be incarcerated, and can be gradually degraded in the human body after 2 months to 5 years, so complicated operations and the injury to organs and tissue, which are caused when the duodenal internal covering membrane is removed from the human body in the future, are avoided, a "rebound" effect achieved after the original barrier is instantaneously and thoroughly dismounted can be alleviated, and the duodenal internal covering membrane can be prepared into a medical instrument which is used for curing obesity and diabetes mellitus and does not need to be removed from the human body in the future； and sinking of a tube-shaped part induced by gastrointestinal motility and jejunum content backflow caused by the increase of a gap between the tube-shaped part (5) of the internal covering membrane and the inner wall of the duodenum can be avoided. The prepared medical instrument for curing obesity and diabetes mellitus can achieve the effects of dropping prevention, removal exemption, rebound inhibition, and injury reduction.
