Multi-Detector Ash Analyzer(AA-D) is an on-line measuring instrument that can continuously detect ash in coal at different locations on the belt. Different from the traditional "single source with single detector" measurement method, by arranging multiple detectors above the belt conveyor, the ash measurement at multiple locations on the cross-section of the belt conveyor can be realized. Therefore, the test result of the analyzer is more representative. The use of multiple detectors can eliminate some "random errors" of the entire analyzer which may affect the detection results. And the accuracy of the detection results is better. Meanwhile, the use of multiple detectors can also effectively reduce the influences to detection result caused by the uneven distribution of the steel wire in the wire belt conveyor and belt deviation. Thus, the instrument is more applicable in the field. For its superior detection performance and field adaptability, AA-D can be widely applied in fields such as coal mining, processing and comprehensive utilization that require fast and accurate measurement of coal ash.