Franz Neumann (1900-1954), a German public law and political theorist, is a peripheral member of the Early Frankfurt School. The reasons of his peripheral membership of the Early Frankfurt School are not only that Neumann has never been in the core circle of the Institute for Social Research, which led by Max Horkheimer and Theodor Adorno, but also that he did his main research in the clues of the German Rechtsstaat Tradition, which is not in the Early Frankfurt School's central project. The importance of Neumann and his research is that he is between Carl Schmitt (and also Hermann Heller), and Jürgen Habermas. In other words, his position could be viewed as a bridge between the Crisis of Weimar Constitutionalism and the post-war reconstruction of the German Rechtsstaat. If we try to understand the development of the German Rechtsstaat Tradition, certainly and absolutely, we could not ignore or look down on Neumann and his research. On the contrary, if we put Neumann and his research in the framework of Early Frankfurt School, not of the German Rechtsstaat Tradition, as a result, we would not understand the background, development and influence of Neumann and his research. It is very pitiful that Neumann's most productive years is in a period of political turmoil. In general, he experienced the Crisis of Weimar Constitutionalism, the rise of Nazi and the reconstruction of Federal Republic of Germany's political life after the World War Ⅱ. However, it is lucky that he did a lot of theoretical and practical works with great enthusiasm in exile. Generally speaking, his thought is among German public law, Marxism and Democratic Rechtsstaat. His analysis and critique of the Late Capitalism, and his idea of Democratic Rechtsstaat are related to and also different from his contemporary scholars. Specifically, this paper tries to reconfigure Neumann's thought, by summarizing and supposing these three questions, what are (1) Why did Weimar Republic fail, (2) What is the nature of Nazi regime, and (3) How to reconstruct the Federal Republic of Germany's political life after the World War Ⅱ. Obviously, although Neumann did a lot of practical works, he is still a theorist after all, and he resolved these three practical questions above in a theoretical way. In brief, he criticized the German Positivism Rechtsstaat in the development of the German Rechtsstaat, interpreted the nature of Nazi regime is Totalitarian Monopoly Capitalism (it is not State Capitalism, which is given by another theorist in the Early Frankfurt School, Friedrich Pollock), and presented the idea of Democratic Rechtsstaat, which is different from the Anglo-Saxon Democracy. Neumann developed his thought, took the key step, which is toward Democratic Rechtsstaat in the development of the German Rechtsstaat, and also presented a basic political framework for the Federal Republic of Germany. Furthermore, Neumann could be simply marked with these three marks below, which are ″ anti-Schmitt's Schmittian,″ ″anti-Orthodox Marxism's Marxist″ and ″anti-Capitalist Democracy's Democrat″. These three marks could not only reveal his three main theoretical origins, but also sketch the core figure of Neumann's thought, namely, what is Neumann's idea of Democratic Rechtsstaat. It is noteworthy that his idea of Democratic Rechtsstaat sublates both the German Positivism Rechtsstaat and the Anglo-Saxon Democracy. In other words, his idea of Democratic Rechtsstaat could be viewed as a general solution (a synthesis) to the problems of modern society. Obviously, we could say that his idea of Democratic Rechtsstaat indicated an approach, which overcame the other narrow approaches. In a very short conclusion, it is very worth pointing out that Neumann took the key step, which is toward Democratic Rechtsstaat in the development of the German Rechtsstaat Tradition, both theoretically and practically. It is misleading that the existing researches about Neumann (especially in China), however, ignore this key step.