Abstract: An evolutionary game model,which is based on the trust evolution and enterprise's entry and exit,is presented to study the trends of cluster's scale with different entry barrier by computer simulation.It is found that cluster evolution can be divided into four stages:growth,shakeout,adjustment and mature,because of the coordination of trust and entry barrier on competition and cooperation.The shape of the curve is an fallen-S. The stable size has inverse ratio with its entry barrier. Also entry barrier has opposite effects on enterprise's entry and survival.

Key words: trust evolution, entry barrier, enterprise’s entry and exit, cluster’s scale