The article focuses on the analysis of the theory of democratic peace - one of the most popular and influential ideas in international relations. The theory argues that democracies not enter into war against other democracies, but peacefully resolve existing contradictions. A world where exist as many as possible democratic states is a peaceful world. The theory encourages and supports democratization in the world, a policy practiced so great by Western powers and international organizations. Meanwhile, some researchers exposed the theory of democratic peace critically and talk about its crisis.