Abstract: Grouting to plug water is a common technical measure for the prevention and control of water disaster in underground engineering and mines. However,the current research on the mechanism of grout propagation and the mining effect lags the practical requirement,which restricts the scientific and effective implementation of grouting engineering. Based on the theory of "deflection effect" of groundwater in fractures,this paper traces the study on the propagation in fractured rock masses,and proposes a scientific hypothesis of the "deflection effect" for the propagation of grouting in fractured rock masses with flowing water in deep underground mines. Two key scientific problems that should be solved for further study are proposed: the mechanism of grout deflection propagation in fractured rock masses,and the mechanism of failure and permeability change of "grouted-rock" composite formed by bias grouting flow. Combined with the research trend,an interdisciplinary comprehensive research method is proposed. It is recommended that future research should take the typical grouting project as the background to study the hydrogeological structure of deep mines and the spatial-temporal evolution of mining,focusing on revealing the deflection mechanism of grout propagation and its influencing factors under dynamic water conditions of fractured rock masses,establishing a mathematical model of grout deflection propagation and an evaluation method for the permeability change due to mining. The result will provide an important scientific basis for the prevention and control of water disaster and safe production in deep mines.