Abstract: A bottle whose bottom can be adjusted to eject air is disclosed. The bottle includes a body, a ball bung and a bottom assembly. The body is of a cylindrical shape and has a mouth and a bottom end. The bottom end is open and provided with an inner thread. The ball bung is used for sealing the mouth. The bottom assembly includes a base, a post and a piston. The post is axially connected on the base. An outer thread is formed on a cylindroid thereof for screwing with the inner thread. The piston is axially connected atop the cylinder and fits snugly into the body to form a gastight status.