This study was designed to comprehend the outline of the epic poetry of the Muong(one of the Vietnamese ethnic minorities) : < The birth of the earth and water >(BEW), and to compare it with the myth of the Kinh(the major nation of Vietnam today). It is believed that The Muong and the Kinh have a common origin, so called the Old Viet. BEW has three main parts. (1)the origin of world the and the human, (2)the origin of the culture, (3)the struggle against the enemy. BEW shows the feature of transitional epic poetry from primitive to ancient. BEW is very characteristic in three points following. The Muong imagined the Holy Tree, instead of the Giant. They thought that the original ancestor was born by the connection of the heaven and the earth. And they thought the human was born from an egg. The myth of the Kinh forms a striking contrast to that of the Muong. In the myth of the Kinh the Giant separated the heaven and the earth, and made configuration of the earth. The myth of the Kinh is still more poor and fragmentary. According to the Kinh the human was created by the Ochuang, the god of heaven. The Giant and the Ochuang seems to be introduced from China during the colonial era. BEW and the myth of the Kinh are common in the idea that the original ancestor was born from an egg in which has several eggs. But the orientation of the motif is not same. In BEW the motif of birth from an egg symbolized the same origin of many. To the contrary the Kinh insisted on their leading role in the establishment of the country. The Kinh also expressed their pride of entering into the medieval age. Establishment of the country, entering into the medieval age, and the flourishing of Buddhism seemed to force the Kinh to keep away from their epic tradition.