"Kasa" is one of the genres of poetic form in Korean literature which had prospered during the period of Yi Dynasty. As a form of rhythmed verse in which its lines can be extended as indefinitely as the poetic ideas reach out,"Kasa"was a great form of Korean literature that succeeded the tradition of Korean poetic literature in Its form of expression as well as its contents. Especially its contents comprehensively include the lyrical full of poetic sentiments, the epic, the instructive, the practical etc., compromising verse with prose into a unique type of literature. Most of its writers were the nobility of that times at first, but as the times changed common people and even women at large participated in writing "Kasa". This form of literature had become a means by which one's ethical life and refined life was expressed and women's spite was vented out. This study is designed to present the following on the basis of various documents concerned: 1) An analysis on the development of "Kasa" literature from its birth to death. 2) A comparative analysis on the forms of "Sijo" and "Kasa". 3) Characteristics of "Kasa" style This kind of "Kasa" literature at last came to an end with the appearance of the new genre of "Chang-ga" at the end Kab-oh Reformation. We come to see, howevere, that through the analyses fo "Kasa" literature we can understand how our ancestors contemplated on the nature and how they attempted to naturalize themselves to the nature.