Our study aims to verify the effects of social relations, opportunistic behavior and trust among partners on the stability of strategic alliance. In order to test the hypotheses, 221 valid questionnaires collected from top managers of 50 strategic alliances in China. Moreover, the results also indicate that contractual governance can moderate the influence of high-level social relations on opportunistic behavior and trust between partners. It is found that the social relationship of senior managers cannot directly affect the stability of the alliance but can negatively affect the opportunistic behavior and positively affect the trust between partners. Opportunistic behavior and trust among alliance partners affect the stability of strategic alliance negatively and positively, respectively. Contract governance can enhance the influence of senior managers' social relationships on opportunistic behavior. In addition, contract governance shows the inverted U-shaped moderating effects on the relationship between senior managers' social relations and trust. Keywords: social relations, alliance stability, opportunistic behaviour, trust, contract governance DOI: 10.7176/EJBM/12-6-11 Publication date: February 29 th 2020