Initial cracking law and evolution law of stress intensity factor at the tip of the branch crack of compression-shear fractured rock under high seepage pressure are discussed. The critical water pressure value and the initial cracking intensity criterion of the fractured rock mass under high seepage pressure are established when tension-shear failure occurs. The cracking characteristics under different water pressures indicate that the existence of osmotic pressure aggravates the growth of branch crack; and the branch crack propagation under high osmotic pressure will convent from stable expansion to unstable expansion and cause the shear failure of the crag bridge at the branch crack tip; simultaneously the branch crack interaction is considered

the crag bridge?s cutting penetration damage mechanical model of the compression-shear rock under the high seepage pressure is established. Finally

the flexibility tensor of the rock mass? initial damage and its damage evolution based on damage mechanical effect of fractured rock are studied. Then a damage evolution equation of fractured rock under high seepage pressure is proposed. The theory provides the basis for the quantitative investigation about the compression-shear destruction of fractured rock under high seepage pressure.