Abstract: Automatic infusion set for continuously infusing liquid medicine of double bottles, including a hollow circular barrel and a float-type sealing valve disposed in the circular barrel. The sealing valve has an I-shaped cross-section for reducing contacting area with inner wall of the circular barrel and preventing the sealing valve from attaching to the inner wall. A rubber-made membrane is disposed on each of two end faces of the sealing valve. An A bottle infusion catheter is passed through the circumference of a lower section of the circular barrel near the cap member at bottom end of the circular barrel, whereby the liquid medicine in double bottles can be automatic continuously infused and it is unnecessary to replace the exhausted drop bottle to save time. Moreover, the air in the vacant drop bottle is prevented from entering the vessels of a patient to lead to thrombosis.