The research subject is The Defense of Beijing in Ming Dynasty, based on “documentary analysis” research methods by using Strategic Study Approach to analyze the Defense of Beijing. This thesis takes four units of the Strategic Study Approach that starts with the strategic environmental analysis in early Ming Dynasty, followed by analysis of both actors. Then evaluates and compares the national power of the two countries. And in the last part will analyze the operation of both sides. Firstly, this study summarizes the internal and external strategic environment before the Crisis of TuMuBoa in the early Ming Dynasty through the collation of historical materials, and connects with the Defense of Beijing that can analyzes its environmental backgrounds. Secondly, the analysis of the actors will be based on both national objectives and political power systems, and summed up the central political power of the Ming Dynasty before the Defense of Beijing by expounding two different levels, national level and the person or group who holds the power (authority level). The analysis of power analysis can be divided into several major aspects including political power, economic power and military power with modern indicators of national power, that can use the qualitative and quantitative analysis to evaluate and compare the power of both states. Lastly, is operational analysis that includes all the strategic study units above, showing how both actors use their respective national powers under the environment. Then, explain the result of the Defense of Beijing and impacts to both states.