Abstract: This paper focuses on the reinforcement material optimization using curtain grouting method during drilling construction for gas extraction. First, the basic water cement ratio of cement based composite material with high ductility is determined based on the viscosity and the compressive strength. Then, the fly ash, silica fume, and polyvinyl alcohol are added to the composite material to investigate the effect of composition ratio on such performances as the viscosity, the setting time, the permeability and the compressive strength. The results show that: the basic water cement ratio is 0.75:1; the water-cement ratio obviously influences the viscosity and compressive strength. The admixture compositions have notable effect on the viscosity of grouting materials, consolidated coal permeability, compressive strength and elasticity modulus；system 1 (fly ash, silica fume and polyvinyl alcohol, 5:15:3 mass fraction) has the optimum grouting effect due to the highest compressive strength, low viscosity and medium viscosity, compared with other systems.