The utility model provides a continuous sealing slagging device for a boiling chlorination furnace. The device comprises a slagging pipe connected with a slagging port of the chlorination furnace. The other end of the slagging pipe is connected with a guide pipe. A nitrogen connector is arranged on the side wall of the guide pipe. The slagging device further comprises a sealed slagging middle tank, the bottom of which is connected with the top of a slag receiving tank through a pipeline. The pipeline is provided with a gate valve. Exhaust gas connectors are respectively arranged at the top of the slagging middle tank and the top of the slag receiving tank. The guide pipe is connected with the slagging middle tank through a connecting pipe. The guide pipe is internally provided with a high temperature valve which is located between the nitrogen connector and the connecting pipe. The slagging device can effectively reduce harmful gases in the slag to avoid diffusion of slag dust and mixed gases in the slag of the chlorination furnace, so that the slag of the chlorination furnace is conveniently treated in a centralized manner, and the economical efficiency, the environment friendliness and the safety for discharging slag by the chlorination furnace are improved. Therefore, the device is simpler to operate, and the field operational environment of operators on the post is extremely improved.