Quaternized poly(phthalazinone ether ketone ketone) anion-exchange membranes were prepared from poly(phthalazinone ether ketone ketone) via chloromethylation and quaternization. The effects of chloromethyl octyl ether quantity on degree of chloromethylation (DCM) of chloromethylated poly(phthalazinone ether ketone ketone) (CMPPEKK) were investigated. ¹H NMR confirmed the structure of CMPPEKK. The properties of anion-exchange membranes with different ion-exchange capacity including water content, area resistance were investigated. The water content of quaternized poly(phthalazinone ether ketone ketone) anion-exchange membrane (QAPPEKK) increased with the increasing of ion exchange capacity. The area resistance of QAPPEKK decreased with the increasing of ion exchange capacity. The energy efficiency of vanadium redox flow battery (VRB) single cell with QAPPEKK membrane reached 85.0%, coulombic efficiency reached 98.5%, and voltage efficiency reached 86.3%.