The invention discloses an automatic detecting system for water level sensors comprising a gas source, a precise pressure reducing valve, an air pressure controller, a host computer, an enclosed air chamber, water level sensors, a converting circuit board and a frequency meter; the host computer is connected to the air pressure controller and reads out the actual air pressure values at the gas outlet of the air pressure controller and the set air pressure value at the gas outlet of the air pressure control according to the protocol of the air pressure controller; the gas source is connected to the air pressure controller after passing through the precise pressure-reducing valve; the air pressure controller is connected to the enclosed air chamber; the water level sensors are connected to the openings of the enclosed air chamber; the electric circuit interface of the water level sensor is connected to the input terminal of the converting circuit board; the frequency output terminal of the converting circuit board is connected to the frequency input terminal of the frequency meter; the host computer is connected to the 485 port of the frequency meter; the host computer reads out the frequency values of the frequency meters according to the MODBUS protocol regularly and successively. By means of the system of the invention, the labor intensity for detecting water level sensors can be substantially reduced and multiple water level sensors can be detected simultaneously so as to increase the work efficiency.