The accurate understanding of the hydrological characteristics of cave dripping water is the basis of studying the groundwater infiltration process in the karst vadose zone. To continuously and accurately obtain dripping water information, this paper designs a dripping water sensor of karst cave to meet the needs of karst hydrogeological study. The piezoelectric induction mode and PVDF piezoelectric film are selected as the induction material, and the heart sound sensor is used as the induction element. Through the analysis of the response principle of the structure design of the extended induction surface, it is verified that the three-layer design could interfere with each other, produce superposition signal and obtain good induction effect. The inductive surface materials of the top layer and the intermediate layer are determined. By simulation in the laboratory and field observation in cave, the precision size of the sensor is designed. The signal processing circuit, software and hardware of embedded system of the sensor are developed to realize the long time monitoring and recording. Cave field data analysis indicates that the induction height of sensor is ≥20 cm, the fastest rate of dripping water is 10 drops per second. It has advantages of precision, stability and waterproof. The sensor is suitable to high humidity cave environment and meets the needs of the related research works.