Abstract: In this paper,from the functional point of backfill materials,the evolution process of backfill technology can be divided into three stages,e. g. ,volumetric backfill,structural backfill and functional backfill. To solve the coupled problems of high-stress,high-temperature and multitudinous-goaf,etc. ,in deep mines,as well as high-cost of backfill mining,an academic idea of Functional Backfill (FB) was put forward. The proposed FB not only can realize the func- tion of traditional backfill,but also can achieve the expanded functions,i. e. ,cold-loading,heat-saving,energy-stor- age,seepage-proofing, etc. More specifically, the concepts of Functional Backfill Materials ( FBM) and Functional Backfill Technology (FBT) were scientifically defined,and the conceptual model of the FBM was established. Then, on the basis of backfill material functions,the functional backfill was classified as Cold Load / Storage-Functional Back- fill Materials (CLS-FBM),Heat Storage & Release-Functional Backfill Body (HSR-FBB) and Cavity-building-Func- tional Backfill Materials ( CB-FBM). Correspondingly,the concepts,functions and basal principles of the mentioned three functional backfills were presented in detail. The application and exploration of functional backfill materials & technologies will further improve the backfill technologies in mines,which have an important and far-reaching impact on the deep mine geothermal co-exploitation,underground goaf reuse and strategic energy reserves,etc.