Researchers in the network security field lack quantitative methods to analysis anti-denial of service (DoS)attacks ability. In this paper, we describe an anti-denial of service testing method based on mobile agent taking on the attacker. The goal of the testing was to evaluate the system and its defense mechanism's anti-denial of service attack ability. The process of testing anti-denial of service attacks can be broadly divided into three phases: DoS attack scenario, information gathering and performance analysis. We describe how the testing process was designed and customized to the defenses, how the performance was measuring, how the tests were run, and what we learned from them about defenses and about testing security system.