In　this　paper,　we　present　a　scalable　dynamic　key　management　scheme　for　wireless　sensor　networks　in　which　new　nodes　can　join　a　sensor　network　securely　and　compromised　nodes　can　be　isolated　from　the　network　in　time.　Unlike　centralized　and　location-based　key　management　schemes,　our　scheme　doesn＇t　depend　on　such　infrastructure　as　base　stations　and　robots.　Thus,　it　possesses　a　higher　degree　of　flexibility.　By　using　a　reasonable　clustering　algorithm,　our　scheme　can　integrate　efficiently　with　the　cluster-based　intrusion　detection　scheme　and　can,　hence,　improve　the　whole　security　of　a　wireless　sensor　network.　Analysis　shows　that　our　proposed　scheme　is　low　in　computation,　communication,　and　storage　overhead.