The present invention provides a method for treating the particle surface of a cathode active material for a lithium secondary battery, the method comprising (a) preparing a cathode active material having a lithium compound; (b) generating a plasma from a gas comprising at least one of a fluorine-containing gas and a phosphorus-containing gas as a part of a reactive gas; and (c) removing lithium impurities present on the particle surface of the cathode active material with the plasma. In accordance with the present invention, the amount of the lithium impurities present on the particle surface of the cathode active material can be reduced to suppress a side reaction of the lithium impurities and an electrolyte.