Relevance of the study. The principle of separation of powers is the most important feature of the rule of law, which confirms the dominance of the legislative branch and the subordination of the executive and judicial branches. The key aspect of the rule of law is a systematic approach to legislation. At the same time, the leading role of law lies in its ability to solve the main and most significant problems of society. To study the concept of separation of powers in a rule of law state. The methodological basis of the study is scientific and research approaches, which include general scientific methods of analysis and synthesis, a historical approach, methods of complex systemic and structural analysis, as well as various methods corresponding to norms, concepts and terms. Thus, the results of the study allow us to draw a number of conclusions. First of all, the concept of separation of powers has long served as the basis for building democratic legal systems. This idea developed at different stages and was closely associated with the works of many famous thinkers and lawyers. The works of lawyers and philosophers laid the foundations that to this day shape our modern perception of the structure of power and its functions. Each stage of the development of this concept reflected social changes and the desire for more just and effective governance.