The article reveals the research methodology of the library space of the Commonwealth of Independent States (CIS) based on the theory of self-organization (synergetics). Synergetics as the direction of post-non-classical science was developed at the end of the last — the beginning of the new Millennium in the works of a number of researchers who proved the universality of this methodology and its applicability to the study of processes occurring in society. However, until the 2000s, this methodology did not get worthy application in the library science. The relevance of this study is that the modern library science requires a new worldview-methodological approach to the investigation of processes taking place in the cultural and library sphere, which will help to develop and enrich the successfully used method of system analysis. Based on this, the author sets the task to study the library space of the CIS as a self-organizing system that is in the process of evolution over a long historical period. The article considers the library space as a dynamically developing system of social nature. The author traces its cause-and-effect relations, conditions and factors in historical perspective and modern aspects. The concept of “library space of the CIS countries” arose after the disintegration of the Soviet Union in 1991 and as a result of formation of the CIS to refer to the form of interstate library interaction and cooperation. The article studies the library space of the CIS countries as a system of interaction of libraries formed in the post-Soviet period, the basis of which is their belonging to the Commonwealth of Independent States, within which the interstate relations of libraries are developing, basing on long historical and cultural ties between them; and the Russian language is the language of professional and interpersonal communication. The author presents the descriptive model of interaction system of libraries of the CIS countries with the main features and principles of construction. The article establishes that the CIS library space is characterized by features of a complex, open, dynamic self-organizing system. The methodological nature and theoretical philosophical significance of the article make it interesting for librarians, science theorists and cultural scientists.