Abstract: The R-ray ash monitor has radiation-related potential hazards and the passive radiation ash monitor is difficult to find effective utilization in various process links of a coal preparation plant. Against this backdrop, the X-ray ash monitor that operates with X-ray instead of traditional radioactive sources is developed. The monitor is upgraded through shifting from a single-point to fan-shaped monitoring pattern and application of “self-learning” to make self-adjustment and optimization of algorithm according to coal quality, making it possible to operate with a greatly enhanced accuracy. Practice shows that for cleaned small coal the standard deviation between the monitored and analytical ash values is 0.21% with the probability of absolute error smaller than the standard error being 66.38% which is increased to 93.97% in case the former is two times less than the latter. The judgement made by the density control system based on the X-ray ash monitor is in good agreement with that by analytical method, with an accuracy being up to 85.71%, and there is no reverse judgement.