To provide a liquid level control system which is easy in the output value adjustment operation of a water level detector, and can control a liquid level highly precisely.

Each detected value from the water level detector 9 and liquid ratio corresponding to a reference liquid level to a lower limit water level and an upper limit water level are stored in a storage means 42. Then, a specific detected value from the water level detector 9 corresponding to a control water level which should be controlled in a tank 1 is transmitted to a detection means 41, after stored in the storage means 42, transmitted to an operation means 43, and calculated to the liquid ratio corresponding to correlation between the lower limit water level and the upper limit water level. The calculated liquid ratio based on the specific detected value is compared, discriminated based on each set water level and water level control algorithm by a discrimination means 44, control signals are transmitted from a control means 46 to each structure equipment of a solenoid valve 4 and a conveying pump 7 via a setting means 45 to control reservoir and supply of water in the tank 1.