Based on field observations, the author proposes a new understanding on the formation of theFirst Bent of the Changjiang River. It is the first time to study the relationship between the formation of theFirst Bent of the Changjiang River and Eocene magmatic activity, suggesting that the First Bent of theChangjiang River is the result from choking of the strong magma activity in Eocene. As a result, theupstream of the river became a natural reservoir, with channel bursting into breach between Mt. Yulong andMt. Haba, making Jinshajiang River run eastward. At the same time, the plateau uplift and the drasticdissection of river channel led to the formation of the Tiger Leaping Gorge. Taking Mt. Yulong as a base,the magnitude of uplifting in the study area (located in the eastern of the Tibetan Plateau) is calculated, withthe magnitude being 3300 m from Eocene to Pliocene, adding 700 m since Pleistocene, totaling 4000 m orso.