Abstract: A one-dimensional (1D) finite-element method (FEM) is proposed to analyze the noise isolating performance of 1D dielectric electromagnetic band-gap (EBG) structure among the power distribution network (PDN) of multilayer printed circuit board (PCB). The 3D structure of the 1D dielectric EBG is simplified as a 1D FEM model, and then the transmission coefficient T, reflection coefficient R and the scattering parameter S are obtained through directly solving the wave equation. The forbidden frequency band gap can be visually determined utilizing the R-T curve, while the noise isolation degree is more conveniently evaluated using S₂₁ parameter expressed in dB. According to the simulated results of the influence on noise isolation performance from the dielectric EBG structure parameters such as the periodic number, permittivity and period length, etc, a two-stage design method is provided for the low-cycle and incomplete band gap EBG structure, namely, at first the band gap is predicted by using the multi-period EBG structure, and then expanding the band gap and enhancing the noise isolation by adjusting the dielectric constant and period length. The rationality of the proposed 1D finite-element method is verified by 3D full-wave electromagnetic simulation.