The electronic properties of CN-adsorbed on Ag electrodes at different potentials have been studied by using the method of self-consistent-charge siscte vasritional Xa (SCC-DV-Xa) chister calculations. It is shown that the binding of-NC-Ag is dominated by both eletrostntic and polarization effects derived from the charge of CN, and that transfer of charge from CN-to silver is the largest donation contribution. The electrode potential influcnces this charge transfer process and the interaction between CN-adsorbate and silver electrode. The results of quantum chmistry calculations fit well with the experimental data of situ spectroscopic studies on the CN-Ag eletrode systems.