Abstract: High ash of coal restricts the high-value utilization of coal. In order to explore the importance of in-depth coal deashing technologies in making intensive utilization of coal resource, the paper first introduces the physical, chemical and biological means—three main technologies currently available, and then goes to elaborate on their respective deashing mechanism, progress of research work so far made, advantages and disadvantages, as well as the type of coal to which each method is adaptable. Finally, the developing trend of the in-depth coal deashing technologies and the efforts that need to be directed in their development are pointed out. The research-derived achievements provide a reference for the further study of coal deashing technologies and high-efficiency and clean utilization of coal.