The invention discloses an impedance design method for a power network of a core chip within a chipset having N input/output (I/O) ports coupled to a voltage source which have an observation I/O port. The method includes calculating a first set of impedances at a predetermined frequency or the observation I/O port, if the voltage source is internally coupled to the N I/O ports within the chipset, and calculating a second set of impedances at the predetermined frequency for the observation I/O port, if the voltage source is externally coupled to the N I/O ports through a carrier coupling the core chip to the voltage source. The first set of impedances to the second set of impedances are compared, and the impedance of the power network or the impedance of the carrier is adjusted according to the comparison result.