This invention discloses a pressure-adjustable extravascular occlusionballoon with drainage and flushing function, relating to the field of vascular hemostasis technology. It includes a tubing wall with a C-shaped front end. Several balloons that can compress each other are arranged inside the C-shaped tube. A ballooncatheter is inserted through the tubing wall, with one end connected to the balloon and the other end extending out from the rear end of the tubing wall. This invention can quickly control massive bleeding, achieving hemostasis without causing permanent loss of blood supply to the controlled blood vessel, thus avoiding related complications caused by ischemia.