Abstract: In China, the problems such as poor sealing quality and serious air leakage for gas drainage boreholes commonly exist in the coal seam and result in the low gas drainage concentration. This limits the development and utilization of coal seam gas. Thus, we propose a new method using a new type of ultra-high aqueous expansion slurry to grout and seal boreholes, and the experiment of condensation and fluidity test of ultra-high aqueous expansion slurry was carried out and the injection of ultra-high aqueous expansion slurry was evaluated. The results show that the setting time of ultra-high aqueous expansion slurry is significantly affected by the water cement ratio and it shows nonlinear growth with the increase of aqueous-cement ratio and can satisfy the time requirement of grouting. The funnel viscosity of ultra-high aqueous expansion slurry increases during the increase of aqueous-cement ratio and the stable slurry which has an aqueous-cement ratio more than 6:1 gets a good injection.