The invention discloses a flood discharge and energy dissipation structure of a narrow valley, a deep tail water and an ultra-large unit width flow curve gravity dam. An overflow dam section of a curve gravity dam is composed of a curve overflow weir and partition piers erected on the weir crest of the curve overflow weir, a flow passing surface hole meeting the flow leakage requirement is formed,a fan-shaped bucket type stilling basin is connected behind the curve overflow weir, and a stilling tail sill is in an arc form and concentric with the dam axis. Wide tail piers are additionally arranged at the tail positions of the overflow surface hole partition piers. The fan-shaped bucket type stilling pool is composed of a straight section and a slope section. The body type of the wide tailpier is T-shaped, Y-shaped or X-shaped, and two-dimensional water flow in a bucket pool can be changed into stable and complete three-dimensional bucket type water flow. The flood discharge and energydissipation structure is simple, practical and convenient to operate, the construction cost can be greatly saved, and the flood discharge and energy dissipation problems of narrow river valleys, deeptail water and ultra-large unit width flow water conservancy and hydropower engineering can be effectively solved.