Abstract: The microfracture activity during the deformation of the sample containing two intersecting model Ⅲ shear faults under biaxial load is experimentally studied using acoustic emission technique. Generally,the microfractures tend to migrate from the cut side to the uncut side of the sample and occur alternately between the two faults. The statistics of focal mechanisms of microfractures shows that the faults with smaller and larger angles to the major principal stress dominate the deformation in the earlier and later stages,respectively. The interaction of the two faults controls the instability of the whole sample.