Abstract: In order to enhance the stability of the heavy medium density for achieving a better performance of the plant's heavy-medium separation system,a test is made with the Amdahl density meter. Field application of the meter indicates that the use of the meter makes it possible to realize on-line regulation of medium density in a more scientific and rapid manner. It works with a control error of ± 0. 005 g/cm³,fully capable of meeting the technical requirement. The successful use of the meter has led to much reduced labour intensity of both sampling and testing personal and significant improvement of coal cleaning performance.