The explosive growth of the Internet and the World Wide Web has made the management tasks such as configuration, monitoring, diagnosis and recovery much more complicated. An automated management system is highly needed to alleviate those tasks of system managers. Some tools use Case-Based Reasoning and Rule-Based Reasoning to do the fault diagnoses. However, they have difficulties in solving problems requiring deep level knowledge. Although some Model- Based diagnostic systems have been developed, they are mainly used to tackle problems in other domains. In this paper, a new model-based automated diagnosis algorithm is proposed. 6 Pages