Abstract: It is used of the float-type, pressure-type, ultrasonic and so on sensors in the observation of water level in China, but the sensors have certain flaws in the practical process. According to the idea of bionics, the TC-401 digital water level sensor uses the thought of the imitation nerve theory. It adapted the develop tendency of the hydrology instruments, and can solve the questions that low instability, the high failure rate, anti-interference and low authenticity in the water level monitor. The paper describes the principle and structure of TC-401 water level sensor and combines with the application on Panshitou Reservoir to study. The research results proved that it can fulfill the need of practical water level to monitor.