Using the finite element method, the stress intensity factor (SIF) of the cracked penal repaired with a multilayered piezoelectric patch is studied. The effects of the parameters, including the voltage applied on the patch, the piezoelectric patch layer and the geometric size of the patch, on the SIF are numerically investigated, based on which the repair efficiencies in different repair parameters are assessed. Based on the results of the numerical models, that the SIF of the cracked panel repaired with a piezoelectric patch is attenuated greatly. Better repair efficiency is obtained with the increase of voltage, but too higher voltage may be unbeneficial. It is beneficial to use more layers in the piezoelectric patch as the thickness of the patch is fixed. The SIF of the repaired cracked panel decreases with the increase of the size of the patch, however, too large patch may not be helpful to elevate the repair efficiency.