Abstract: Following an introduction to the structural design, working principle and technical features of the NGAM-2008 gamma-ray ash monitor, as well as an analysis of the effect of its application in the filter-pressing system of Gaoyang Coal Preparation Plant, the ash measurements obtained at varying speeds of the belt of transfer conveyor are compared. Result of field application shows that the monitor can measure the ash content of coke product on a continuous basis with the measured result well reaching the expected target, and its measured value can serve as a basis for effectively guiding the operation of the flotation circuit. It is indicated through comparing the measured results at different belt speeds that the greater the belt speed, the larger the fluctuation of measured data becomes.