Abstract: Coal gasification slag is a solid by-product produced by the coal gasification process, which has certain utilization value but is difficult to complete separation. As an efficient method for separating unburned carbon from coal gasification slag, flotation can utilize the difference in surface hydrophobicity between inorganic matter and unburned carbon. Coal gasification fine slag sample from a chemical industry in Ningxia was collected as the research object to investigate the energy consumption during the flotation process of coal gasification slag with different particle fitness. Different grinding frequencies were set to control the particle fineness, and the agitation speed of flotation machine was adjusted to regulate the energy consumption. Flotation results indicated that with the grinding frequency increasing, the particle size became finer and required greater energy input to achieve better flotation results. For example, when the fineness of coal gasification slag was -45 μm accounting for 93.20%, the best flotation effect was achieved with an effective power of 1.76 W and the tailing burn loss was 14.33%, and when the fineness of coal gasificationslag was -45 μm accounting for 98.08%, the effective power of 30 W flotation effect was better, then the tailing burn loss reached 3.33%, which met with the standard of first-class ash applicable tobuilding materials.