The corrosion behavior of Immersion Silver (ImAg) finished Printed Circuit Board (PCB) in mold environment was studied using Scanning Kelvin Probe (SKP) technology. The mold growth behavior was observed by using stereo microscope and SEM, and the corrosion product was analyzed by EDS. Based on the results of SEM and EDS, mold could grow on the surface of PCB-ImAg specimens under hygrothermal condition, Aspergillus niger shows higher activity and has a priority growth characteristics. The activity of mold is a promoter in the localized (pore) corrosion process and the leakage of copper of PCB-ImAg covered by mold. SKP results show that the PCB surface potential as a whole increases with time. And the colony region of PCB occurs preferentially corrosion as the anode; then the corrosion product area enlarges gradually. Although the corrosion reaction generates small amounts of toxic Ag⁺, which inhibits the growth and metabolism of the spores, this do not prevent the corrosion of PCB-ImAg caused by mold from occurrence. ImAg finished technology is unable to completely inhibit the growth of mold on PCB surface, which could not fully meet the requirement of PCB anti-mildew.