The Doryon-Line is the lowest line of the Chechori and Dangeu and the length of the Chechori and the Dangeu have wide influence on the Doryon-Line. Also the change of the Doryon-Line is re-lated to the proportion the length the depth that is the curved proportion and the two curved proportion 0.04 and 0.13 are related to the roof style of the traditional architecture in Chosun Dynasty. The Chosun people have made a change the Doryon-Line monotonous in the 14C-15C but the Doryon-Line have been full of variety every fifty years in the 15C-18C. Especially Chosun people have been at war in the mountains and fields in the Doryon-Line are 0.06 and 0.07 in this period I think that the curved proportion 0.06 and 0.07 are symbolized the natural beauty in the mountains and trees of the Korea.