This paper proposes a cooperative protection system with a multi-agent system, which could adapt protection functions to the complicated changes in the power system automatically and intelligently. In the cooperative protection system, multi-agent system allows the cooperation between plural numbers of equipments. Some agents stay in one place and collect local power system information such as current and voltage data. Other agents move about to utilize data or functions installed in other equipment. The cooperation of multi-agent enables the flexible utilization of all hardware resources by any equipment, so that various adaptive protection functions are realized. Simulation of the proposed method has been applied to some typical protection function, i.e. overcurrent protection function. The results showed that the cooperative protection system could achieve the optimum protection capability. Although many practical aspects need to be thoroughly studied, it is quite promising to realize the adaptive protection using the multi-agent technology.