Abstract: Coalition is an important cooperative method in multi\|agent systems. Most of the methods don’t consider evolvement of coalition, so it is difficult to avoid a mass of computation, and assumption about coalition value known isn’t realistic. In the paper here, equivalence of coalition and mechanism of evolvement are presented, which can obtain solution of coalition by non\|computing of coalition value and may reduce computational complexity. The work of the paper introduces equivalence and evolvement of coalition, and releases restriction of assumption about coalition value known, compared with the work of Shehory ＆ Kraus.