Intragastric bag provided with safe inner bag and piezoelectric sensor and introduction device

The invention relates to the technical field of devices, which can be implanted into human bodies and be used for treating obesity. Anintragastric bag comprises a shell (2), which is expanded to form an outer bag (3); an expansion bag (4), which is expanded to form a safe inner bag(5); a shunt plugging device (6), which is capable of forming a plugging cavity (6i); a piezoelectric sensor (7), which is embedded into a niche (6h) at the outer side of the tube wall of the shunt plugging device (6); and a fastener (8), which is used for fastening a port of the expansion bag. The intragastric bag is characterized in that through the shunt plugging device, partial space of the outer bag (3) is occupied by the safe inner bag (5) and the partial space and the safe inner bag (5) are mutually isolated, even the shell (2) is ruptured, the safe inner bag (5) can be used for preventing the shrunken shell (2) from entering into intestinal tract to cause intestinal obstruction, and meanwhile, pressure drop in the outer bag (3) can be sensed by the piezoelectric sensor(7)and a signal is transmitted, so that an in-vitro signal receiver (12) can give an alarm, and dye liquor in the outer bag (3) is extruded out of the intragastric bag(1) and is discharged out of the body through urine.