Objective To explore the effect and timing of exchange transfusion on the treatment of pertussis in hyperleukocytemia. Method? The?effects?of?exchange?transfusion?and?other?treatments?in?pertussis?children?with?the?highest? white?blood?cell?count?(WBC)?of?>50×109/L?were?retrospectively?analyzed.?Results? A?total?of?72?children?with?pertussis?(24? boys?and?48?girls),?with?the?highest?WBC?of?>50×109/L?were?studied.?They?were?divided?into?the?exchange?transfusion?group?(17? cases)?and?the?non-exchange?transfusion?group?(55?cases).?Compared?with?the?non-exchange?transfusion?group,?the?interval?from? onset?to?admission?was?shorter,?the?incidence?of?severe?pneumonia?and?heart?failure?was?higher,?and?the?highest?WBC?was?higher? in?the?exchange?transfusion?group?(P<0.05).?The?distribution?of?the?highest?WBC?was?statistically?significant?different?between? the?two?groups?(P<0.01),?and?the?proportion?of?the?highest?WBC?≥70×109/L?in?the?exchange?transfusion?group?was?higher.?The? decrease?rate?of?WBC?in?children?with?the?highest?WBC?≥70×109/L?in?the?exchange?transfusion?group?was?higher?than?that?in?the? non-exchange?transfusion?group,?and?the?difference?was?statistically?significant?(P<0.05).?When?the?ROC?curve?of?the?highest? WBC?was?plotted?to?predict?pertussis?death?in?the?non-exchange?transfusion?group,?it?was?found?that,?at?the?optimal?critical?value? of?WBC?71.9×109/L,?the?sensitivity?and?specificity?of?the?prediction?of?death?were?80%?and?90%,?and??AUC?was?0.89?(95%?CI: 0.74~1.00,?P=0.004).?Conclusions? Exchange?transfusion?is?an?effective?treatment?to?reduce?WBC,?but?its?effect?on?improving? clinical?symptoms?is?not?clear.?When?WBC?is?(50~71.9)×109/L,?other?indicators?need?to?be?considered?for?whether?exchange? transfusion?should?be?applied.?When?WBC?≥71.9×109/L,?transfusion?therapy?may?be?required.?