Abstract：Hydraulic fracturing of core of earth-rockfill dam is an important issue related to the safety of the dam，and it attracts much attention. In this paper，the achieved results show as follows：(1) the conditions of hydraulic fracturing should include at least two conditions—physical one that includes fissures existing in core and low permeability of core material，and the mechanical one that is enough larger“water wedging”action；(2) the mechanical mechanism of hydraulic fracturing can be explained with the theory and method of facture mechanics；(3) the boundary and stress conditions of laboratory，field or model tests should be similar to those in up-stream face of core of the dam，for instance，some fissures should be included in sample，and the water pressure should be forced from the surface of the sample；and (4) the numerical simulation to the development course of hydraulic fracturing is deformed and the effective way to study the hydraulic fracturing in core of earth-rockfill dam is to reveal the induced condition and mechanical mechanism，to develop reasonable criterion and to estimate and simulate by using numerical analyses.
