Abstract: The formation mechanism of dynamic Agent coalition is an important direction of current research on MAS. In order to overcome the shortcomings of the present formation mechanism of dynamic Agent coalition， such as low utilization ratio of Agents, a new formation mechanism of dynamic Agent coalition based on “twoBidding /Tender” and NOAH planning is proposed. The mechanism uses “twoBidding /Tender” to form dynamic coalition and uses NOAH planning to decompose tasks. It can fully exercise parallel implementation capacity of Agents while meeting the time constrains of subtask. It also enables agent to join in or withdraw from the coalition dynamically. Thus the utilization ratio of Agents is improved, and the interests maximization of selfinterest Agents is guaranteed. Its validity is proved by a classical example.

Key words: Agent coalition, bidding and tender, NOAH planning, task decomposition