The invention relates to a negative-pressure gas exhaust and water slag discharge device which comprises an exhaust pipeline and a water slag collection tank. The water slag collection tank is connected with the exhaust pipeline by being connected with an exhaust pipeline pup joint. The bottom of the water slag collection tank is provided with a water slag discharge tank. The lower end of the water slag discharge tank is provided with a water slag collection sleeve. The two ends of the water slag collection sleeve are communicated. One end of the water slag collection sleeve is fixed to the lower end of the water slag discharge tank through a fastening ring. The other end of the water slag collection sleeve is suspended in the air. The lower end of the water slag discharge tank is provided with a cross bar. A spring is arranged on the cross bar. The upper end of the spring is provided with a hollow ball valve. When water slag does not exist in the water slag collection tank, under the action of negative pressure in the water slag collection tank, the water slag collection sleeve automatically closes and shrinks to be airtight, and it is guaranteed that the interior of the water slag collection tank is airtight and the air can not enter the water slag collection tank. When the water slag exists in the water slag collection tank, under the action of negative pressure in the water slag collection tank, the water slag collection sleeve will be opened to start to discharge the water slag under the action of gravity of the ware slag and the action of water permeation, it is guaranteed that the air is prevented from entering the water slag collection tank while the water slag is discharged, and the problem of gas leakage is solved. The device has good market value.