As　the　key　component　of　heat　pipe　cooling　reactor,　heat　pipe　has　the　advantages　of　high　heat　transfer　efficiency　and　excellent　isothermal　performance.　The　high　working　temperature　of　alkali　metal　high　temperature　heat　pipe　has　broad　application　prospects　in　the　thermal　protection　of　hypersonic　vehicle,　space　nuclear　reactor　cooling,　solar　energy　utilization　and　so　on.　At　the　same　time,　the　high　temperature　heat　pipe　can　also　be　applied　to　the　radiation　heat　dissipation　system　of　space　nuclear　power　system,　the　main　cooling　mode　of　nuclear　powered　unmanned　underwater　vehicle　and　the　waste　heat　removal　device　of　advanced　reactor　system.　It　is　the　best　choice　with　high　heat　transfer　efficiency　and　high　safety,　and　can　effectively　meet　the　heat　dissipation　requirements　of　the　nuclear　power　system　of　future　military　and　civil　equipment　systems,　overcome　the　shortcomings　of　complex　structure　and　insufficient　passive　safety　of　traditional　nuclear　power　system.　In　a　word,　as　a　kind　of　heat　transfer　device　with　high　thermal　conductivity,　the　core　part　of　heat　pipe　lies　in　the　evaporation　and　condensation　of　its　internal　working　fluid.　If　there　is　non-condensable　gas　in　the　gas　cavity　during　the　working　process　of　the　heat　pipe,　the　steam　and　non-condensable　gas　in　the　main　flow　area　will　move　to　the　gas-liquid　interface　together　under　the　action　of　convective　motion.　The　existence　of　non-condensable　gas　hinders　the　normal　condensation　of　the　working　fluid　at　the　gas-liquid　interface,　shortens　the　effective　length　of　the　heat　pipe,　and　breaks　the　isothermal　property　of　the　heat　pipe.　The　area　where　the　non-condensable　gas　accumulates　is　called　the　＇inactive＇　area　and　has　poor　thermal　conductivity.　Therefore,　in　order　to　accelerate　the　in-stack　application　of　high　temperature　heat　pipes,　the　degree　of　influence　of　non-condensable　gas　on　the　heat　transfer　characteristics　of　high　temperature　heat　pipes　is　a　major　problem　which　is　urgent　to　be　settled　and　evaluated.　In　this　paper,　a　non-condensable　gas　area　heat　transfer　model　was　added　based　on　the　thermal　resistance　network　method,　and　the　effect　of　non-condensable　gas　on　the　steady-state　heat　transfer　characteristics　of　high　temperature　lithium　heat　pipes　was　studied.　The　results　show　that　with　the　increase　of　the　volume　fraction　of　non-condensable　gas,　the　temperature　of　non-condensable　gas　area　decreases　more　greatly;　with　the　increase　of　the　input　power　of　the　evaporation　section　of　the　heat　pipe,　the　higher　the　overall　temperature　of　the　normal　working　area　of　the　heat　pipe,　the　smaller　the　volume　fraction　of　the　same　mass　of　non-condensable　gas,　and　the　position　where　the　temperature　gradient　of　the　heat　pipe　wall　decreases　obviously　moves　downstream　with　the　increase　of　power.　©　2022,　Editorial　Board　of　Atomic　Energy　Science　and　Technology.　All　right　reserved.