Abstract: In this paper,an attack knowledge model that can be applied in the initiative defense architecture is proposed,and the model’s practicability,re-useability and extendibility are achieved. The attack knowledge is described using attack knowledge description language（AKDL）,and the data,operations and relations of attacks are modeled based on object-oriented technology. An AKDL to C++ compiler is used to compile the attack knowledge in AKDL language into C++ source code of attack component object,then the attack knowledge library（AKL） is implemented,which can provide the attack knowledge to the various security modules through APIs.