Abstract: The high carbon content of coal gasification residue and the mutual restriction of carbon ash hinder the resource utilization of coal gasification residue. Therefore, decarbonization is the basis of resource utilization and high value utilization of coal gasification slag. Due to the developed pores on the surface of coal gasification slag, the main decarburization methods, such as flotation and oil agglomeration, have the problems of high drug consumption and low carbon recovery rate. The high internal phase W/O emulsion is an oil−in−water emulsion with the volume of the internal water phase greater than 74.05%. The internal water phase replaces the oil to fill the pores on the surface of the coal gasification slag, which greatly reduces the fuel consumption. The properties of coal gasification slag samples were investigated by industrial analysis, X−ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of surfactants, internal water ratio and inorganic salts on the stability and particle size of high internal W/O emulsions were studied by laser particle size analyzer and optical microscope. Finally, the decarbonization effect of high internal phase W/O emulsion with kerosene, diesel and SPAN80−oil mixture on coal gasification residue agglomeration was compared with the oil saving rate and carbon residue recovery rate. The results show that the fixed carbon content of the sample is 51.94%, and the main gangue minerals are quartz, calcite and anhydrite. The addition of alkali lignin, surfactant, NaCl and MgCl₂ can improve the stability of the emulsion. Compared with kerosene, diesel oil and SPAN80−oil mixture, the recovery rate of residual carbon in high internal phase W/O emulsion oil was increased by 14% on average, and the fuel saving rate was over 85%. Among them, the high internal phase W/O emulsion with 85% internal water, 25% surfactant and NaCl added has the best decarburization effect, and the recovery rate of carbon residue can reach 91.23%. The results show that high internal phase W/O emulsion oil agglomeration is an effective method to decarbonize coal gasification slag.