Triboelectricity has demonstrated bright application prospects in the field of blue energy harvesting. However, the low output efficiency of solid-liquid triboelectricity hinders its practical application. This paper proposed a high-efficiency drip nanogenerator with a cambered surface based on the brachistochrone curve principle. In this nanogenerator, a drop of water can achieve an output current of 50 µA and an output voltage of 137 V without pre-charging. The cambered-surface structured triboelectric nanogenerator (C-TENG) enhances the short-circuit current by 30 times compared to the traditional TENG based on flat-surface structure (F-TENG). The output power of C-TENG reaches up to 1.875 mW at the central angle of 60°. The Simcenter STAR-CCM+ Viewer software is utilized to simulate the falling process of water droplets and the dynamics to explain the difference in the falling process of central angle structures at different central angles. The C-TENG characteristics ensure improved energy collection efficiency. Therefore, it is used to design a new droplet energy collection structure for rain energy harvesting. C-TENG has a more significant lighting effect than F-TENG. This new drip generator demonstrates remarkable efficiency in collecting various water energies in nature and has potential applications in device power supply and self-powered sensing.