A bionic whisker sensor (BWS) based on flexible friction nanogenerator is designed to help autonomous underwater vehicle (AUV) sense the surrounding environment information. The sensor generates electrical signals through the contact and separation between the fluorinated ethylene propylene film and the conductive ink, and estimates the direction, location and size of the external load by analyzing the collected electrical signals. In order to demonstrate the practicability of the sensor, the whisker sensor is placed in a circulating water tunnel to test its underwater sensing ability. The experimental results show that the sensor can sense the flow field information including the flow velocity and the oscillation frequency caused by the vortex.