Although the solid–liquid triboelectric nanogenerators have made great progress in energy harvesting, their efficiency is fundamentally limited by the continuous shielding effect of the solid–liquid electric double layer (EDL). Herein, a liquid-jet triboelectric nanogenerator that exploits Plateau-Rayleigh instability (PR-TENG) is demonstrated to overcome this barrier. PR-TENG converts low-frequency water flow into high-frequency droplets, avoiding shielding effects from continuous flow and achieving a contact-separation frequency of ≈50 Hz. At a flow rate of 320 mL min−1, the PR-TENG generates an output current of over 100 µA, ≈120 times the magnitude of conventional single-electrode droplet TENGs (D-TENGs) that rely on electrostatic induction. The operational mechanism of PR-TENG arises from droplet-fusion-induced triboelectrification, surface charge trapping, and charge redistribution, enabling energy harvesting from continuous water flow and water-level monitoring applications. This work significantly improves the electrical output performance of flow-based triboelectric nanogenerators and provides an effective solution for continuous flow-based energy harvesting.