Abstract: In order to realize the "zero emission" of coal gasification technology, it is necessary to solve and develop the environmental protection and safe utilization of gasification slag. The residual carbon of gasification fine slag is the solid waste produced by coal gasification technology, and its comprehensive utilization is an important factor for the whole coal chemical industry project to realize circular economy. In this paper, carbon materials with porous structure were made by using residual carbon from gasification fine slag as carbon precursor and KOH as activator. Firstly, the effects of different mass ratios of carbon to alkali (1:1, 1:2, 1:3, 1:4) on the structure and electrochemical properties of the prepared carbon materials were investigated and compared. The results showed that the activated gasification fine slag residual carbon (CK-2) obtained at 500℃ for 90 mins in N2 atmosphere and under the condition of the mass ratio of carbon to alkali 1:2. has better electrochemical performance. When the current density is 0.5 A/g, the mass specific capacity of CK-2 reached 86 F/g, showing good rate performance. The mass specific capacity of CK-2 was about 1.5 times higher than that of untreated residual carbon. The reason might be that under the condition of activation, on the one hand, KOH reacted with inorganic minerals such as silicon-aluminum oxide, and the content of inorganic minerals was reduced by acid washing and increased the carbon content; on the other hand, KOH reacted with active carbon atoms to form pores in the material in real time and resultantly modified polar oxygen-containing functional groups. Secondly, the selected activation material CK-2 was used as an active material to assemble a symmetrical capacitor. Under the current density of 2 A/g, the energy density of the supercapacitors reached 4.72 Wh/Kg. After 10000 cycles, the capacitor could keep 89% of the initial value, showing excellent energy density and cycle stability.