The invention relates to a quantum key distribution (QKD) method and a quantum key distribution network system. The quantum key distribution method comprises steps that a center end used for quantumcommunication with various user ends is established, and the center end and the various user end adopt a key distribution scheme based on a Blom scheme and the QKD. One center end or a plurality of center ends can be provided. A quantum channel can be established between each pair of center ends, and a QKD protocol is executed between the center ends to combat DoS attacks; furthermore, a block design is adopted to form a quantum key distribution network. When the key distribution network is attacked by quantum rejection service, corresponding key distribution schemes can be provided by aiming at damages caused by different DoS attacks. The costs of the quantum key distribution can be reduced, and the safety and the expandability of the quantum key distribution can be improved.