Abstract: The attack of Distributed Denial of Service（DDoS） has become one of the most harmful problems in network security.There are some limitations in traditional defendant for using the single method.This paper proposes an initiative defence model which adopts mobile agent and integrate multi-defense methods.The elements of the mobile agent in defense model are designed in detail to solve the limitation of the single defense method，passive defense and high false alarm.The model is robust and scalable.

Key words: mobile agent, Distributed Denial of Service（DDoS）, detection, defense

摘要： 分布式拒绝服务（DDoS）攻击已成为网络最大的安全威胁之一，传统检测防御方法由于多采用单一防范措施很难对其彻底防范。利用移动Agent特性，在设计上整合多种防御方法，构造了一种综合的主动检测防御模型，并详细设计了模型中移动Agent的组成元件，力求解决存在的单点失效、被动防御等问题，使得该模型具有良好的健壮性和可扩展性。

关键词: 移动代理, 分布式拒绝服务攻击（DDoS）, 检测, 防御