Abstract: Influenced by faults,the mechanism of rock movement was different due to the underground excavation in hangingwals and footwalls of faults.Theoretical and numerical methods were used under two construction states of underground excavation in hangingwalls and footwalls of faults.It was indicated that when the steep faults in the tensile deformation region were incurred by underground excavation,no matter the excavation in hangingwalls or that in footwalls of the faults,there would be additional tensile stress on the vertical fault plane and the shear strength decreased,showing the characteristics of normal fault slip.This phenomenon would appear on the ground surface in the form of fault escarpment,and down to the fault "activation"——the lower limit of fault slip section where the fault throw gradually reduced to zero.