企業何以形成聯盟，一直是學者探討策略聯盟的重要議題。而聯盟動機，則為促成聯盟形成的重要因素。過去已有諸多研究探討聯盟動機，亦發展出許多相關理論，如交易成本、資源依賴理論。誠然，聯盟動機為聯盟形成的重要成因，但具備聯盟動機的企業一定會形成聯盟？末形成聯盟的企業必無聯盟動機？本研究以企業成本－效益決策觀點為理論基礎，針對聯盟動機理論與社會關係理論進行整合性探討，期能對聯盟形成有更完整的了解。經由實證結果，本研究發現：聯盟動機為企業加入聯盟的預期效益，而預期效益儘管對聯盟意願有正向影響，但企業聯盟形成實為聯盟預期效益與知覺成本評估後的結果，故在知覺成本的負向影響下，企業儘管具備聯盟動機，卻未必會形成策略聯盟。此外，在如何降低知覺成本以提升企業聯盟意願的議題上，社會關係理論則扮演一定角色。本研究期能對聯盟形成建立起更完整分析架構，並提供給實務界欲籌組聯盟的企業相關參考建議。

In prior research, the formation of alliances is an important issue of strategic alliance, and alliance motivations are important factors affecting alliance formation. Prior research has led to valuable insights on the alliance motivations, and contributed to full exploration, like transaction cost theory and resource dependence theory. Truly, alliance motivation is an important factor affecting alliance formation, however, is motivation the only one to cause the formation alliances? Is there no any motivation once the business wouldn’t Join alliances? In order to discuss the alliance formation completely, this article integrates alliance motivation theory and social relationship theory in the perspective of the cost-benefit decision theory. This research finds: alliance motivation is regarded as expected benefit of alliance formation. Although expected benefit have positive effects on the formation of alliances, alliance formation outcomes is the assessment of expected benefit and perceived cost. The negative effect of perceived cost will cause the business unwilling to join the strategic alliance. Furthermore, how to reduce perceived cost to promote the business joining strategic alliance, social relationship theory plays an important role. This study attempted to build up the research framework of the formation of alliances and provide the practices suggestions about forming alliance.