Electrochemical detection of trace arsenic(III) in aqueous phase was studied with a porous gold (PAu) electrode, which was prepared by paper-based templating method. Square wave voltammetry was performed in As(III) solutions. The limit of detection of 0.1 ppb was obtained with a linear detection range of 0.1-14 ppb, which complies with the regulations for As(III) content in drinking water. The analysis of roughness factor and diffusion coefficient showed that the porous structure of the PAu electrode might have a stronger contribution to improving the sensitivity and selectivity of the target ion, compared to bulk gold electrode.