Decompression diffusion furnace mouth sealing device

The utility model discloses a decompression diffusion furnace mouth sealing device which comprises a quartz plate which is arranged at one end of a furnace gate and is adhered to the end surface of a quartz tube, wherein a back plate is arranged on the outer side of the quartz plate; a cylindrical shell is arranged between the back plate and the quartz plate; a thermal-insulating element is filled into the space surrounded by the cylindrical shell, the back plate and the quartz plate; the mouth of the quartz tube is sleeved by a sealing flange; a first-stage sealing structure is arranged between the sealing flange and the inner side surface of the back plate; a second-stage seal is formed between the quartz plate and the end surface of the quartz tube; a transition sealing chamber is formed between the first-stage sealing structure and the shell, the sealing flange and the inner side surface of the back plate. According to the decompression diffusion furnace mouth sealing device disclosed by the utility model, the transition chamber is formed, and a protecting gas is filled into the transition chamber, so that negative pressure process pollution is prevented.