Pit-type gas nitriding furnace adopts energy-saving furnace liner with double water-cooled furnace cover, vacuum rubber seal and temperature control in the upper and lower two or more zones. The nitriding furnace's thermal insulation, furnace temperature uniformity, sealing performance and nitriding speed are greatly improved, and the furnace type is consistent with international standards. The outer casing of this series of well-type gas nitriding furnace is welded by steel plate and section steel. The lining of the furnace is made of ultra-lightweight, high-strength energy-saving refractory bricks. The outer layer of the lining is sandwiched with aluminum silicate fiber and filled with expansion insulation powder. The heating element is wound into a spiral shape by a high-temperature resistance wire, and is installed on the brick lining of the furnace liner, and a stainless steel vacuum tank is installed in the furnace chamber. A double-headed stainless steel drip device is installed on the furnace cover for dripping methanol to make the temperature atmosphere in the nitriding furnace uniform. The furnace cover is equipped with a sampling tube, an exhaust pipe, and an input pipe on the upper side of the furnace tank wall for ammonia gas input. The furnace tank and furnace cover are sealed with water-cooled vacuum rubber, and are equipped with compression bolts. The exhaust gas in the gas nitrogenation furnace is discharged out of the furnace through the exhaust pipe.