The United Nations is the largest, most extensive, most representative and influential worldwide political and economic organization established after the Second World War. The United States, on the other hand, was the main ally of the anti-fascist war in the Second World War and the superpower with the strongest post-war strength and the widest participation in world affairs. The United States has deep ties with the United Nations. The United States is the main designer, participant and leader of the United Nations, whose main purpose is to maintain post-war peace and stability.

During the Cold War, the United States and the Soviet Union mainly maintained balance and could not unilaterally break the rules and balance.

After the Cold War, American peacekeeping policy has been evolving with the change of four presidents. During the Bush administration, the United States pursued a radical United Nations peacekeeping policy, and peacekeeping operations were mainly carried out within the United Nations system. During the Clinton period, the United States implemented a selective United Nations peacekeeping policy and an effective unilateral peacekeeping policy. During George W. Bush's period, the United States pursued a negative United Nations peacekeeping policy and advocated a positive unilateral peacekeeping policy. After Obama took office, he advocated a smart UN peacekeeping policy and a diversified unilateral peacekeeping policy. It can be seen that the evolution of American peacekeeping policy after the Cold War not only reflects the political and foreign policies of successive presidents, but also reflects the strong unilateralism of American peacekeeping. Although the emphasis of American peacekeeping policy is different in different historical periods, the evolution of American peacekeeping policy after the Cold War has three common characteristics: flexibility, practicality and contradiction. The main reason for these characteristics is that the fundamental purpose of American peacekeeping policy is to maintain the world political and security order dominated by the United States. The evolution of American peacekeeping policy is not only the expression of American foreign policy, but also the result of the interaction of various domestic factors and changes in the international environment.

World peace and security have always been a concern of people all over the world, and international peacekeeping operations have injected fresh blood into world peace and stability. Since the founding of the United Nations, people have been paying attention to the United Nations peacekeeping operations, ignoring the policies and guidelines of the United States, Russia, France, Britain and other big countries in peacekeeping operations. In fact, in the international system composed of sovereign countries, the peacekeeping policies of world powers have a decisive impact on United Nations peacekeeping operations and world peace and stability. As the largest country in the world, the adjustment and implementation of its peacekeeping policy is particularly important for world peace and stability. American peacekeeping policies can be divided into three types: one is the United Nations peacekeeping policy, which is aimed at United Nations-led peacekeeping operations; Second, the mandatory peace policy formulated by the United States and authorized by the United Nations but led by the United States and its allies; The third is the stable action policy implemented by the United States alone without the authorization of the United Nations. The United States attributes both the compulsory peace policy and the stable operation policy to the peacekeeping policy, which is the characteristic of the American peacekeeping policy. In short, the United States peacekeeping policy includes the United Nations peacekeeping policy within the United Nations system and the unilateral peacekeeping policy outside the United Nations system.