Abstract: In order to solve the problems of easy plugging, high reaction temperature and high material cost of ordinary high-water materials in the process of mine filling and mining, fly ash was mixed into high-water materials to study the initial setting time, water precipitation rate, seed setting rate, compressive strength and reaction temperature of high-water materials under different water-solid ratios and different fly ash contents. The hardened slurry was analyzed by scanning electron microscopy and its microstructure was observed. The results show that when the water-solid ratio is fixed, the initial setting time of high-water material increases with the increase of fly ash content, and the order of increase is water-solid ratio 1.5∶1 > 1∶1 > 2∶1; when the content of fly ash is fixed, the initial setting time of high water material increases with the increase of water-solid ratio, and the increase amplitude is approximately linearly related. Different water-solid ratio and fly ash content mainly affect the strength and internal temperature of hardened slurry. Among them, the water-solid ratio is 1∶1 and the fly ash content is 60 %. The strength of the material increases from 2.1 MPa to 2.8 MPa with the curing time. The internal reaction temperature of hardened slurry is reduced by 12.3 ℃ compared with that without fly ash, a decrease of 31.77%; the minimum cost of hardened paste with comparable strength decreased by 54.6% compared with the blank group. The research results can provide reference for the performance research and engineering application economy of high water material with fly ash.