The study of the relations in spreading and influence among different countries' literature has always been the focus in the field of comparative literature. In the development of comparative literature studies, French school and American school attached great importance to "positivism", the fact-based relations and paid little attention to the area of "variation". In fact, variation due to the differences of culture, ideology, reader/translators' personal interpretation is quite common and inevitable in the process of communication and dissemination of the literature among different civilizations. Therefore, the variation study of comparative literature undoubtedly pioneers a new study thought for the comparative literature study and at the same time, enriches and develops the comparative literature theories and research methodologies. From this point of view, variation study is a new theoretical breakthrough for cross-civilization study as well as a major theoretical innovation for the development of comparative literature theories. [ABSTRACT FROM AUTHOR]