Abstract: Following an analysis of the problem encountered in measurement of raw coal ash using radioactive ash monitor at coal preparation plant,the paper elaborates on the structural make-up,working principle and technical features of the NGAM-2008 natural gamma-ray ash monitor. As evidenced by analysis of the result of its field application at Luling Coal Preparation Plant,the monitor is remarkable in performance which is well up to the requirement of the plant. As there is no need to use radioactive source,its application corresponds to the needs for green,environmentally-friendly and safe operation.