The frequent water gushing in sandstone mining strata of Luohe Formation has seriously affected the safety production of the mine. The traditional grouting systems are faced with the problems of serious percolation effect and uncontrollable gelation performance，which is difficult to achieve effective regulation of fissure water. In this work，the microscopic characteristics of sandstone pores were clarified by analyzing the mineral composition and microscopic morphology of five typical natural core samples， such as gravel-bearing sandstone， giant sandstone， coarse-grained sandstone， medium-grained sandstone， and fine-grained sandstone. A solid-free gel system with low cost and excellent stability was constructed for grouting. The injectivity and plugging performance of the gel grouting system were studied by physical simulation displacement experiment. The pore distribution characteristics in the core before and after grouting were studied by nuclear magnetic resonance online displacement experiment. The results showed that the small pore diameter and poor connectivity were the geological reasons for the difficulty of smooth injection and long-distance migration of the traditional grouting systems. Due to the existence of percolation effect，the curing and plugging effect of traditional grouting system was obviously lower than that of theoretical design. A novel gel grouting system with low cost，solid-free，good injection，and long-distance migration performance was constructed by using 0.5%—0.6% polyacrylamide，0.6%—0.7% organic amine monomer crosslinking agent，0.07%—0.08% phenolic monomer crosslinking agent and 0.2%—0.3% organic acid regulator as raw materials. The gel grouting system could achieve gelation within 48 h，meanwhile， had no obvious dehydration within 180 days，showing excellent long-term aging stability. The gel grouting system had good injectivity. The pressure attenuation ratio was 7.85% —20.95% ，meanwhile，the plugging ratio was 82.04% —92.19% after continuous flooding. The gel grouting system increased the seepage resistance and blocked the subsequent fluid by occupying the large channel or fracture space，which realized the effective plugging of the water layer. The research results could provide new ideas for the grouting and water plugging construction of sandstone in Luohe Formation sandstone.