Abstract: This paper proposes an idea of pouring gasification ash into the underground goaf as a grouting fire prevention and extinguishing material. In order to effectively solve the problem that the gasification ash slurry of coal-based oil tends to block the pipeline in the process of grouting, the influence of three suspension agents such as xanthan gum, carboxymethyl cellulose（ＣＭＣ） and sodium soil on the suspension rate and fluidity of gasification ash slurry was studied through a series of experiments. The results showed that with the increase of the amount of suspension agent, the suspension rate of slurry increased gradually, and its fluidity decreased gradually. More specifically, when the addition amount of xanthan gum, CMC and sodium-soil was 0.25%, 1.5%and 3%, respectively, the suspension rate reached the maximum with 81.82%, 72.73% and 53.24%, respectively. Among the three suspending agents, xanthan gum has the best suspending effect on gasification ash, followed by CMC and sodium-soil. The fluidity experiment showed that the fluidity of the slurry was the worst with adding xanthan gum to the slurry, which is not beneficial for the pipeline transportation of the slurry. While sodium-clay is added to slurry, the fluidity of the slurry is the best. But it is prone to water-cement separation and blockage of the pipe. Hence, considering suspension rate and flow, CMC was selected as suspension agent.