Abstract: It is found with microscopic observation that under uniaxial compression,when the rate of axial strain changes from 10-2/s to 10-8/s or the pressure is constant,the failure status of gabbro samples shows significant variation. This phenomenon indicates that the time interval △t from the start of the external force acting on the rock to the complete failure of the rock may affect the failure status in the rock. Further investigation of this phenomenon may improve our understanding of the process of earthquake occurrence.