A method of target assignment in multi-aircraft cooperative air combat based on distributed calculation was put forward according to the characteristics of the present air combat.Referring to the present three-level command system of air force we built up the corresponding hierarchical structure of decomposed task and Multi-Agent System (MAS) target assignment model.Then simulation was made for the air combat of typical multi-formation against multi-target which proved the effectiveness of this method.Finally the virtues of this method in improving air combat efficiency and reducing assignment time were analyzed.