Abstract: In order to realize accurate measurement of liquid level of material tank of flotation system in the presence of accumulated layer of secondary foam, a special liquid level meter capable of making detection of the real liquid level in tank is developed by the mine’s coal preparation plant. The meter consists of a pull-wire displacement sensor and a counterweighted ball float. The ball float can penetrate the foam layer and float on the real liquid surface and the upper/lower travel of the ball float is measured by the displacement sensor in a real-time manner for detecting the real liquid level. Practice shows the use of the meter can lead to elimination of inaccurate measurements caused by the presence of accumulated foam layer on liquid surface and reduced rate of faults of various electrical and mechanical equipment. Its use has met with a great success, which provides a sound basis for turning the plant into an intelligent one.