To　study　the　thermal　characteristics　of　Gas-Controlled　Sodium　Heat-Pipes,　experimental　system　was　developed　at　National　Institute　of　Metrology.　Including　Gas-Controlled　Sodium　Heat-pipes,　furnace　and　temperature　control　system,　high　temperature　vacuum　degassing　system,　pressure　control　system,　and　high　precision　temperature　measurement　system.　Experimental　studies　on　temperature　stability　and　uniformity　were　carried　out.　The　results　show　that　temperature　stability　within　±0.84　mK　in　15　minutes,　with　pressure　controlled　at　7840　Pa,　655°C.