在今天的讀者看來，余光中是一位詩人兼散文家，他在六十年代初期提出的散文革新主張，直到現在仍受重視。然而在一九六三年之前余光中主要是以詩人的面貌在文壇出現，他的散文絕大部皆是誠論和藝評，符合他後來標舉的現代散文條件的，嚴格說來一篇也沒有。余氏飲譽文壇的《鬼雨》、《逍遙遊》等散文，在在一九六三年中他的散文革新宣言發表後，才陸續登場。本文試圖把余氏的散文主張放在歷史脈絡中觀察，探究余氏由詩人而向散文領域拓展的原委，並考察這一轉變怎樣塑造了余氏的散文主張，並奠定了他後來在文學界的地位。

In the eyes of today’s readers, YU Kuang-chung is a poet and a prose writer. His novel ideas on prose writing, first raised in the early 1960s, still attract attention. Yet, prior to 1963, Tu was mainly regarded as a poet. Most of his prose written in this period were critiques on poetry and fine arts. Strictly speaking, not a single piece of these works fulfils the criteria of Yu’s later definition of modern prose. Yu’s most celebrated prose such as Guiyu (鬼雨), Xiaoyaoyou(逍遙遊)were written only after he had published his revolutionary proposition in 1963. this paper launches a historical investigation into the reasons why Yu tried his hand at a genre new to him and how this change of literary identity shaped his proposition.