Considering the environmental, limited traditional natural resources and power demand pressure, there is a great need to involve the distributed energy resources (DER) to the existing central power plant. So this paper proposes the multi-agent based distributed energy system, which incorporates traditional central power plant and different DER by using Multi-agent system (MAS) technology. A new three layered MAS architecture with good generality is designed, which can be used in small, medium and large scale multi-agent based distributed energy system (MAS-DES). The cluster and super cluster are defined to work as virtual power plants in the medium and large scale case. It also presents the novel architecture for single agent system with learning ability. Moreover, the reliability of Multi-agent system is assessed by Bayesian Statistics. The proposed MAS-DES uses the traditional and renewable resources in a more reasonable way and provides a better solution for the power supply considering the cost, pollution index and reliability. ©2009 IEEE.