Abstract: Denial-of-Service(DoS) attacks are the main puzzles in the security of Ad Hoc network.A novel agent-based security routing protocol scheme was proposed to block DoS attacks.Agent can update itself at some interval by the trustworthiness of the neighbor nodes to fit the Ad Hoc distributed routing computing environment.It can efficiently improve trustworthiness and decrease computing complexity.Agent security specifications were extracted by the feature of the attacks.NS2 simulator is expanded to validate the security routing protocol.Simulation results show that agent-based security scheme is highly effective to detect and block DoS attacks.