Theories of international regimes have explained the creation, maintenance, and decline of international regime. However, their explanations on changes of international regime are much more different one another. For example, the theory of hegemonic stability argues that international regime can be created and maintained by hegemonic state and will be declined if the hegemonic state decline. On the other hand, the functional approach believes that the positive functions and effects that international regime provides motivate states to create and maintain the regime, while the game theoretical approach explains international regimes based on cost-benefit calculation of rational states. Thus, this paper compares and contrasts the arguments of the three major theories of international regime and applies the approaches to the case of the Nuclear Non-Proliferation regime. In particular, this study examines the role and strength of the Nuclear Non-Proliferation regime in East Asia to test the specific arguments of the approaches. In conclusion, this paper will assess the relative explanatory power of each approach based on the analysis of the changes of the Nuclear Non-Proliferation regime.