This study is focused on interpreting the background of formation, the formal characteristic and a poetic world of the work-Gosan Yoon Sun-do`s UBOOSASISA. The summary of this study is as follows; 1. Yoon Sun-do had lived a succeeded-banished-sequestered life, but had established an original view of literature on account of recepting Buddhism and Taoism over his typical Confucianism, and so he had n a great work-UBOOSASISA through these ideological foundations. 2. The Uboosasisa is a work of Yeonsijo consisted of forty stanzas on four seasons. It is a song of fisherman and has regular repetitional structure. 3. The poetic world of this work is as follows; 1) Criticizing $quot;Cramped(局促之缺)$quot; in former Ubooga, he pointed out that it had been resulted from integration of old poems. He expressed his opinions concretly about the former Ubooga as follow; $quot;Disharmony with sound(音響不相應)$quot; in the musical aspect, $quot;Lack of deep meaning(語意不甚備)$quot; in the literary aspect. 2) Gosan had been in the natural spaces, he had enjoyed them as playing ones in appearance, and also had recognized them as ways of expressing his conflicts.