Abstract: In order to prevent the toxic and harmful gas from spreading to the outside of the gasifier through fractures of surrounding rock,and ensure the safety of the gasification process, a roadway filling process was presented based on the basic properties of super high-water material.Firstly，an auxiliary filling pipe and an exhaust pipe were laid out at the maximum elevation of filling roadway roof and extended to the outside of the airtight wall before the roadway was sealed.Then, the airtight wall is constructed at the end of the tunnel, and the filling pipe is connected with the auxiliary filling pipe. Finally, the mixed slurry was poured into the roadway after the filling preparation work was completed, and the filling operation was finished when the mixed slurry was flowed out from the exhaust pipe continuously. The process was used to fill some roadways of gasifier in Shanjiaoshu UCG program. The results show that the filling rate is over 91%, which means the strong fluidity of super high-water material meets the requirement of roadway filling; the existence of roadway slope is conducive to the flow of filling slurry,which can improve the filling rate;there is only one exhaust pipe in each of the filling roadways, and the air could gather in the top of roadways.In addition, the reasons for the burst of filling pipe, frequent start and stop of injection pump,and the precipitation of the slurry occurring in the filling process are analyzed, and the corresponding improvement measures are given.