Tseng Kuo- fan’s theory of literature is based on his method of yang-ch’i and realized in his way of hsing-ch’i. This paper, having pointed out the importance of ch’i in Tseng’s Collected Works and his views on the immortality of writing, is divided into two parts. PartⅠdeals with the maintenance and nourishment of ch’i in the light of its twofold implications. Tseng maintains his physical strength through chün-i ch’en-lao, and nourishes his ch’i by way of chin-te hsiu-yeh. Ch’en-lao means constant exercise of one’s sinews and bones, and chün-i refers to the elimination of care and thought. Chin-te relies on great aspiration (chih) while hsiu-yeh means taking pain with one's work. The effect of chin-te hsiu-yeh is seen in the gradual refinement of the quality of one’s ch’i. Once nourished, ch’i can help broaden one's mind and immortalize one’s writing. PartⅡdwells first on the implication of hsing-ch’i and then on its relationships with creative and critical writing. To Tseng, creative writing requires both natural endowment and knowledge. One’s natural endowment, which remains unchangeable throughout one’s life, deffers in the yin-yang and kang-jou. A writer wishing to immortalize his works should know his own natural inc1ination. He must acquire his knowledge extensively and discriminatively. And in the process of writing, he must be careful with the diction, tone and structure of his work. Because of his promotion of naturalness, Tseng objects to piling up senseless words or plagiarism so as to allow the easy flowing of ch’i in writing. As regards critical writing, Tseng following Yao Nai’s lead discusses writing according to the theory of yin-yang and kang-jou. Before he puts the theory into practical app1ication, however, he tries to make quite a few modifications, and it eventually results in the book, The Four Phenomena of Classical Writing. Among the four phenomena, he favors most the “extreme masuline force,” which he also utilizes as the yardstick to measure the quality of writing. Judging from Tseng's comments, we know that the ch’i in a peice of writing can best be recognized through careful reading and discrimination.