The　operational　flexibility　of　coal-fired　power　plants　has　become　a　priority　objective;　however,　the　lifetime　main　devices　is　reduced　due　to　thermomechanical　fatigue　during　transient　processes.　This　study　focuses　on　t　safety　of　high-pressure　heaters　at　operational　flexibility　measures.　The　dynamic　characteristics　of　therrr　parameters　in　the　1#　HP　heater　were　obtained　and　analyzed　based　on　transient　models　of　a　coal-fired　pow　plant.　The　change　trends　of　pressure/temperature　on　the　steam/feedwater　side　of　the　1#　HP　heater　at　thr　throttling　the　extraction　steam　measures　were　different　with　that　at　the　feedwatcr　bypass　measut　Subsequently,　finite　element　analysis　method　was　used,　and　the　thermomechanical　stresses　under　the　fo　measures　were　calculated　and　analyzed.　The　time　to　reach　the　maximum　mechanical　stresses　was　shorter　th,　that　of　thermal　stresses.　Finally,　the　fatigue　lifetimes　of　the　heater　were　estimated.　The　maximum　fatigue　dama　ratio　at　the　per　load　cycle　was　0.0069%,　and　the　minimal　allowable　number　of　cycle　was　14413　in　the　upp　region　of　the　tube　sheet　when　the　extraction　steams　of　#1,　#2,　and　3#　HP　heaters　are　regulated　simultaneous)　The　study　could　offer　data　guidance　to　the　safety　and　maintenance　of　coal-fired　power　plants　during　operatior　flexibility　regulations.