The 64th section (Wuneng works hard on Thorn Ridge; Sanzang talks of poetry in the Wood Immortals' Hermitage.) of Journey to the West is more unexplainable than the other sections. Ancient and modem scholars have a lot of arguments about the final ending of the story which the tree was chopped. However, there still exists unsolved uncertainties in audiences' minds. The author proposes that the story is deeply related to the contradiction between Zen and Poetry. All the fiends are the reflection of the Sanzang's contradictive emotion facing the poetry effusion. Actually, the death of the tree fiend insinuated that Sanzang should control the motive of writing poems. This article is anticipated to solve the difficult problem for several decades: ”Why does the tree fiend have to die?”