Abstract: In this paper, taking Pan’er Mine as an example, through the construction of underground fly ash water-saving filling system, we carry out the filling for tunnel and end of mined-out area to reduce the loss of cold and wind flow in the working face, so as to realize the heat damage treatment. The system mainly includes the preparation of transportation system of fly ash slurry, slurry mixing system, air duct foaming system three parts, which has the characteristics of resource saving, low cost, no chemical pollution, high reliability, safe and efficient and so on. The system can not only realize the rapid transport of large amount of fly ash, but also solve the problems of high water-cement ratio of grouting slurry, foaming application of large amount of fly ash and recycling of water resources. In addition, the roadside filling process and the end filling process are proposed and well applied in the field.