Built-in anti-backflow device for drainage system

The utility model relates to the technical field of anti-backflow devices, and discloses a built-in anti-backflow device for a drainage system, which comprises a cylinder body, the top of the cylinder body is fixedly sleeved with a mounting ring, a pull rod penetrates through the outer edge of the mounting ring, the inner wall of the cylinder body is provided with a sliding chute, the inner wall of the sliding chute is connected with a connecting block in a sliding manner, and the connecting block is connected with the top of the cylinder body. And a sleeve is fixedly assembled at the bottom of the barrel. According to the anti-backflow device for the sewage pipe, through the arranged supporting rods, limiting cylinders, pull rods and clamping plate devices, when the anti-backflow device is installed or blocked, a user can pull the pull rods to enable clamping plates to move, so that the inner wall of an installation ring and a clamping groove in the sewage pipe can be in butt joint or the installation ring c