Abstract: Frequency properties of return path impedance between power/ ground planes in a multilayer printed circuit board (PCB), which contains only one signal via were investigated. At the same time, some shorting vias were applied to reduce the input impedance of multilayer PCB. Power/ ground planes form a radial transmission line structure and the input impedance at antipad acts as return path impedance of signal current between power/ ground planes. PMC (perfect magnetic conductor) boundary condition was defined on the periphery of power/ ground planes, and exciting current was applied on the antipad hole, the axial electric of shorting vias are zero and then an efficient 2D boundary element method was used to solve the electromagnetic problem. The calculated frequencies for the return path input impedance of power/ ground planes is up to 10GHz. The obtained results show that addition of some shorting vias between in the two plane which have same characteristics can reduce input impedance, in addition, the input impedance appears capacitance or inductance alternatively with the variation of frequencies, whose value can reach upon several hundred ohms at anti-resonant frequencies, moreover, the input impedance can be represented by static capacitance or static inductance at low frequencies. The algorithm and calculated results were validated by finite-element software based on full wave analysis.