The present disclosure provides a boosting control method of an engine for cylinder de-activation (CDA). The method includes: a CDA operable area confirming step of determining, by a controller based on a driving state of the engine, whether the CDA is in an operable area after the engine starts; an actual boosting deriving step of deriving a total target boosting from the controller and calculating the desired actual boosting; a supercharger operable area confirming step of determining, by the controller, whether the supercharger is in the operable area; a supercharger target rotation speed deriving step of deriving, by the controller, a target rotation speed of the supercharger; and a supercharger passage opening step of closing a bypass valve to open a supercharger passage.