Abstract: In recent years，surface subsidence and ecological environment problems caused by coal mining have become increasingly prominent，and coal mine filling mining technology has become an impor⁃ tant way to achieve safe and green mining. The traditional filling materials have the problems of poor con⁃ solidation performance and high cost，and the large amount of fly ash as filling aggregate can not only im⁃ prove the phenomenon of slurry segregation and bleeding，but also realize the utilization of solid waste re⁃ sources. Based on the practice of a coal mine filling project，the workability，mechanical properties and en⁃ vironmental safety of high - volume fly ash filling materials were systematically studied. The results show that whether high-volume fly ash is used as filling aggregate or fly ash + coal gangue is used as filling ag⁃ gregate，the workability of slurry，the strength of sample and the leaching concentration of characteristic heavy metals all meet the requirements of mine filling，and the strength of sample continues to increase in the later stage. The large amount of fly ash as filling material has good engineering application prospects.

Key words: fly ash, coal mine filling, working performance, mechanical properties