This paper shows the possibility to use the oxidized porous silicon (PS) as a transducer material for ion sensor application. It aims to study the over Nernstian behavior of the porous material towards the concentration of sodium ions in contact. We have studied the dependence of the PS sensitivity on the porosity of the samples, which are prepared from a lightly doped silicon substrate, Then, we have presented a model to explain the mechanism of the ionic species adsorption at the electrolyte/SiO2 interface, and to interpret the observed large sensitivity against the different concentrations of the cations. The reproducibility of the sensor response and its lifetime were satisfactory for a frequent use.