Abstract-During this period, study on ethno-religious group relations is more focused on the conflicts that occur between them. This condition then has implications for the many theoretical reviews about it. Theories that discuss about ethno-religious group conflict are very easy to find in various social science literatures, including psychology. In contrast to ethnic-religious group conflict, study about harmony of ethno-religious group relation are still rarely done so that it implies to the lack of theoretical reviews about it. Even if there is a theory, it does not explain comprehensively. Although, as a discipline, psychology has actually offered some theoretical concept that explain comprehensively about harmony of ethno-religious group relation. This paper aims to inform the public that the psychology, especially social psychology has long been concerned about harmony of ethno-religious group relation. Contact Theory, Cross Cutting Categorization Theory, Common Ingroup Identity Model Theory, and Cooperation and Competition Theory are some social psychology theories that discuss about harmony of ethno-religious group relation which will be describes systematically and concise in this paper.