The article examines the process of changing the economic paradigms in economic science. It is shown that all known theories became coexisting in parallel with each other, the modern image of economic theory changed completely, knowledge became limited and fragmented. It was investigated the nature of historical changes in economics, based on the theories of different economists of the world economy. The main achievements of economic science of the XX century, and the problems of changing paradigm in the economic theory are also analyzed in this paper. The article demonstrates the issue that modern economy is the knowledge-based economy. The main driven forces of modern economy changed completely. For better managing knowledge economists should overestimate the principles of the world economy.