A new model for the impedance of porous materials was developed. The transmission line model with pore size distribution (TLM-PSD) is based on the transmission line equivalent circuit, considering the effect of pore size distribution (PSD). The PSD was represented by an analytical distribution function, for example, the log normal distribution, With this model, impedance was a sole function of the representative penetrability alpha(mu) when the standard deviation a is constant. Phase angle at low frequency or high penetrability changes from -90 degrees at sigma = 0 to -45 degrees at sigma = infinity. This indicates that a wider distribution leads to more porous characteristics of impedance. Experimental impedance data of a gold powder electrode were successfully fitted with the TLM-PSD,