After Cold War, global governance becomes the important research field of international relations, especially the context of its formation, operation and impact on international community. Moreover, under the context, the hegemony system goes growing, mature or decline? It also makes a great impact on international relations theory and comparative political study. This article try to research hegemony system, and analyze how U.S. maintain its hegemonic role in 1992-1995 Bosnia Civil War and 1998-1999 Kosovo War.