Abstract: To explore the application of the gas-controlled heat-pipe in metrology,the thermal characteristics of the gas-controlled sodium heat-pipe furnace is researched.The best temperature control position of the furnace is found without pressure control,the temperature stability and uniformity both in the single thermometer well and among different thermometer wells are studied,and two different winding modes of heating wires are discussed.Experimental results show that the temperature stability reaches ±0.836 4 mK within 15 min,controlling heat-pipe inner temperature at 655 ℃,and the gas line pressure at 7.840 kPa.