The purpose of this article is to reassess the reform ideas and activities of Kim Ok-kyun & Pak Yna-Hyo as the leaders of the Enlightenment Party carried out a coup d`tat in December 1884 in order to build a modern state upon the model of the Western nation-state during late 19th century Chosen`s national crisis, in the view of the development of their political visions, leadership and influences. In the late 19th century Korea, Yi Dynasty had to undertake the following urgent tasks in the face of changing international relations: externally, it had to defend its national independece from the neighboring powers, and internally, it needed to increase national power by uniting the people and carrying out reformist policies to create a `strong army and rich nation`. Since early 1880s, the Enlightenment Party tried to contact western diplomats and Japanese leaders in order to achieve national goals such as national independence from Ch`ing(China) and utilize the power of Japan, actually approximated with aspects of the `balance of power`. In spite of the failure of the coup d`etat, they continued the reform efforts during their long exile in Japan, and wrote ` Reform Memorial of 1888` to suggest specific reform ideas and plans on the building of a modern state in late 19th century Chosen. To reform the despotic monarchy of 19th century Chosen, they broke from the traditional notions that a state belong to the king of a dynasty, divided the operations of the royal family and the executive, insisted that the power and rights of the king should be reduced and restricted by the law. At that time they aimed to transform the ignorant, uncivilized Korean people into a modern, civilized nation able to resist the despotism and invasion of foreign nations, and to enhance the basic rights and liberties of the people in order to encourage the participation of the public in politics. We need to pay close attention to their reforem plans and activities in the following aspects: first, their perceptions of 19th century Western modern, civilized nations and their concrete reform plans; second, their attempts to internally integrate the subject of the reforem movement; and third, the mobilization and participation of masses. It is now possible to draw implications from their experience, in that they noticed the problems arising as a result of changes to the international and domestic order, they comblined tradition and modernity by a complex fusion, and introduced a model and blueprint for the reform movement aimed at building a modern nation-state.