The utility model provides a nitrogen gas humidification system which is used for adjusting the dew point of an annealing furnace. The nitrogen gas humidification system comprises a water tank, a liquid level control device, a temperature control device, a water replenishing valve, a nitrogen gas supplementing valve, a nitrogen gas outlet valve and an electrical heater, wherein the water tank is connected with the liquid level control device, the temperature control device, the water replenishing valve, the nitrogen gas supplementing valve, the nitrogen gas outlet valve and the electrical heater respectively.