Abstract: Following an introduction to the background of the application of the natural γ-ray ash monitor at the Handan Coal Washery, and the working principle, structural design and technical features of the monitor, an analysis is made of the effect obtained through application of the monitor at the washery based on the result of comparison of the analytical ash value and monitor-detected ash value. Field application result shows what: the monitor can work remarkably well with a high efficiency provided that it is checked, maintained and calibrated on a regular basis and is not subject to the influence of external factors; its use can better meet the requirement for determination of the ash of raw coal from different mines, and timely provide accurate ash data for process control and coal cleaning operations; the ash data provided by the monitor can serve as a reference for internal business settlement; and it merits widespread application.