Modern power system is a complex, open and distributed system. Multi-agent is a new technology of distributed artificial intelligence. It is easy to make the distributed systems run well. The basic principles and the applicable scopes of Multi-agent are described in this paper. Especially the various applications of Multi-agent in power system are introduced, such as security-defense system, secondary voltage control, electricity markets, EMS and power plant. The further studying works of Multi-agent are schemed. The the studying ways in control system, adaptive ability and foreground on wide control fields of power system. applications of the other fields in power system are described, intelligence, communications are pointed out and especially the foreground on wide control fields of power system.