Ku Sang was born in Seoul in 1919 and died there on May 11, 2004.  When he was a small child his family moved to the north-eastern city of Wonsan, where he grew up. His parents were Catholics, his elder brother became a priest but Ku Sang underwent a crisis of faith during his student years in Japan, where he studied the philosophy of religion, and he only slowly found his own understanding of Catholicism. He returned to the northern part of Korea and began work as a writer and journalist, but after the Liberation in 1945 he was soon forced to flee to the south because of his refusal to conform to the ideological standards of the Communists when he tried to publish his first volume of poems.

He was for many years an editorialist for the Kyonghyang Newspaper in Seoul. His first poems were written while he was a student in Japan and he has steadily written and published volumes of poetry, as well as essays on social, literary, and spiritual topics, he has also written a number of plays, and edited literary anthologies. The volume Even the Knots on Quince Trees . . . contains poems evoking his life's progress through the agonies of modern Korean history.

His poetry is marked by a rejection of the refined symbolism and artificial rhetoric found in the often more highly esteemed work of poets such as So Chong-ju. Instead, Ku Sang oftem begins his poems with the evocation of a personal moment of perception, in the midst of the city or of nature, and moves from there to considerations of more general import, where the poem frequently turns into a meditation on the presence of Eternity in the midst of time. A number of poems refer to the poet's struggle with tuberculosis, but many are hymns celebrating the wonder of being alive. Ku Sang has spoken out clearly on the ecological issues that are now popular, pinpointing the pollution of the Han River as not only a crime against nature but as a symbol of the moral corruption of contemporary humanity.

Ku Sang's work has always found a welcome among readers eager for poetry that addressed the essential meaning of life and sang the simple experiences of truth that mark the poet's own life. The apparent simplicity of Ku Sang's poetic world has meant that until quite recently his work was undervalued in the world of critical opinion. It is now recognized that in Ku Sang, Korea has produced a major religious poet of great originality and utter personal integrity, the authenticity of whose vision is attested by the publication of translations of his poems in French, English, German, Italian and Japanese.