The　once-through　heat　recovery　steam　generator　(HRSG)　of　gas-turbine　combined-cycle　power　plants　adopts　a　triple-pressure　reheat　evaporator　arrangement.　To　study　the　overall　performance　of　the　evaporator　during　operation,　it＇s　divided　into　three　sections:　EVA1,　EVA2,　and　EVA3　along　the　working　fluid　flow.　In　this　study,　in　accordance　with　the　heating　load　distribution　characteristics　of　the　evaporator　and　in　consideration　of　the　system　mass,　momentum,　and　energy　conservation　equations,　the　nonlinear　mass　and　pressure　drop　balance　equations　are　directly　solved.　The　flow　distribution,　pressure　drop　distribution,　profiles　of　working　fluid　temperature　and　outlet　steam　temperature　of　evaporator　at　boiler　maximum　continuous　rating　(BMCR),　75　%　BMCR,　and　30　%　BMCR　loads　are　analyzed.　The　flow　distribution　of　evaporator　at　each　load　shows　a　positive　response　characteristic.　The　flow　distribution　at　all　levels　is　relatively　reasonable,　and　there　will　be　no　heavy　difference　in　the　temperature　and　steam　quality　of　fluid,　which　will　lead　to　pulsation.　Simulation　results　demonstrate　that　the　metal　properties　can　meet　the　requirements　of　material　strength　at　each　working　condition,　and　the　evaporator　will　not　experience　flow　instability,　stagnation,　and　pulsation　at　low　loads.　The　triple-pressure　once-through　reheat　HRSG　can　operate　safely　and　reliably　and　has　the　advantage　of　lifting　and　lowering　the　load　rapidly.　©　2022　Elsevier　Ltd