Abstract: Thoroughly researching liquid-solid contact electrification can significantly enhance our understanding of liquid energy harvesting, chemical processes, and geological mechanisms. However, this research is challenging because liquid changes dynamically, the interface chemistry is complex, and there are few rapid and simple measurement methods available. In this study, a liquid-solid triboelectric nanogenerator was developed as a probe to successfully quantify the charges with varying polarities at the liquid-solid interface. Owing to the design of two spatially arranged electrodes, this proposed probe was able to quantify the interfacial charges within a mere 50 ms propelled by the significant electrical potential difference between the liquid and the electrodes. By concomitantly analyzing the charge signal and short-circuit current signal, the probe is utilized for detecting the flow state of the liquid. Finally, the probe has been demonstrated to be applicable for liquid energy harvesting. This study presents a promising approach to address the challenges of liquid-solid contact electrification research and provides a novel perspective for enhancing our understanding of the chemical processes at liquid-solid contact electrification.