In　order　to　investigate　the　thermo-hydraulic　characteristics　of　working　fluids　in　the　coolant　channel　of　nuclear　thermal　propulsion　reactors,　the　flow　and　heat　transfer　performance　of　high　temperature　and　high　velocity　hydrogen　in　the　circle　tube　was　studied　by　the　numerical　calculation　method.　Comparing　with　the　experimental　data,　it　is　found　that　the　pressure-based　coupled　algorithm,　SST　k-ω　turbulence　model　and　hydrogen　property　model　are　reasonable　and　feasible　to　simulate　the　flow　and　heat　transfer　performance　of　hydrogen　at　high　temperature　and　high　velocity.　The　calculated　values　agree　well　with　the　experimental　data,　and　the　numerical　simulation　model　is　correct.　Based　on　the　analysis　of　flow　and　temperature　field　of　the　base　case,　the　effects　of　thermal　parameters　on　the　flow　and　heat　transfer　performance　of　hydrogen　were　also　studied.　The　increasing　inlet　mass　flow　rate　enhances　heat　transfer　performance　and　the　increasing　heat　flux　weakens　it.　The　methods　and　results　can　provide　some　references　and　guidance　for　the　study　of　the　flow　and　heat　transfer　performance　of　gaseous　fluid　under　high　temperature　and　high　heat　flux,　and　thermal　design　and　simulation　of　nuclear　thermal　propulsion　reactor.　©　2020,　Editorial　Board　of　Atomic　Energy　Science　and　Technology.　All　right　reserved.