Abstract: To mitigate PCB(printed circuit board) power/ground impedance, which is a great negative influential factor to signal and power integrity of high-speed multilayer PCB , the relation functions among PCB power/ground resonant impedance,resonant frequency, resonant quality factor and the electromagnetic parameters of power/ground planes structure were deducted based on cavity resonant model. According to the deductions above, two main ways to reduce PCB power/ground resonant impedance from the aspect of selecting conductive and insulating materials whose electromagnetic parameters are more helpful to reduce power/ground impedance were developed. These two ways include using conductive material with high permeability and low conductivity and adopting insulating material with high permittivity and loss tangent. The latter full-wave simulation results prove the effectiveness these two ways.