This article focuses on reasons for changes in international monetary and financial systems and on the role of Law in the establishment of the International Monetary Fund (IMF) and its activities. The article proves that discrepancy between international monetary and financial systems and development level of international monetary and financial relations was the main reason of these systems' evolution. State governments realized how insufficient self-policing of international exchange relations is, and how necessary is the substantial state intervention in their regulation and this realization contributed to the establishment of IMF, granting it the ability to execute according functions, which let states to establish certain international legal order in the monetary and financial spheres.

It is concluded that international legal science played a special role in the establishment and performance of the IMF, its regulatory importance, foundation of global legal order.

World wars were just an impulse to change international monetary and financial systems. It is concluded that the role of legal science grows in conditions of current rampant development of integration and internationalization of the world economy, that is why it is vital for both lawyers and economists to continue their research of efficiency of the IMF performance - to - quality changes in international economic relations ratio, since the IMF could not succeed in preventing global economic crises, which have recently been shaking almost all countries, including the most developed ones.