A coating device for sealant is disclosed. The coating device includes a sealant storage pipe provided with two end portions; one end portion is connected to a gas jet means and the other end portion is connected to a nozzle; a pipe wall (5) of the sealant storage pipe is made from a flexible material; and the pipe wall (5) can be subjected to recoverable inward deformation perpendicular to an axial line of the sealant storage pipe. A coating system and method employing the coating device are disclosed.