Abstract: Instabilities of strategic alliances relate to sharing of proprietary core resources.A specialization theory model indicates that spillovers with the core resources sharing can break ex balance of competition,although it can bring economies of division to and enhance competion abilities of alliances members.Thus it brings the inherent tension between cooperation and competition in alliances,and also causes to alliances instabilities simultaneity.When information is symmetric,the cooperative conflict which causes instabilities to alliances can be described by a"prisoner’s dilemma",and when information is asymmetric,optimal spillover is a result of the contingent decision based on the anticipation for spillover levels of other member’s and the ex ante competitive ability ratio.Because of incentive incompatibility,when cooperation isn’t a believed commitment and when the prices in market undulate,alliances disintegrate.

Key words: strategy alliances, propriety core resources, cooperation, spillover, instabilities