Abstract: To protect the system promptly and effectively when an intrusion was detected, a mobile agent based automatic intrusion response system was advanced. The response plan was automatically created and the mobile agents were sent to the hosts that are attacked to disable accounts, close ports, make the speaker aloud and shut down the host. Response agents can also reconfigure firewalls. The implementation of a response plan was monitored and the plan can be adjusted dynamically. The prototype of the system was used in the dynamic network defense system of Jinhang network. The running result shows that the mobile agent based intrusion response method is much more effective.