Abstract: In order to enhance the rationality about the coalition utility allocation among agents and the stability about forming the global optimal coalition in multi-agent system,this paper proposed a coalition formation strategy based on loyalty．The new strategy introduces the conception of agent’s loyalty,determines if one agent leaves the coalition before finishing the task or not during agent taking part in a coalition every time,and consequently evaluates the agent’s loyalty．At the same time,the new strategy decides the coalition utility allocation by means of combining each agent’s loyalty and their ability to finish the task．Theoretical analysis and experiment results show that the novel strategy can improve the justice of allocation for utility and achieve a global optimal solution,which is stable,speedy and simple.

Key words: Multi-agent system (MAS),Coalition,Utility allocation,Loyalty