Electrochemical water disinfection, which is based on anodic oxidants evolution such as chlorine, has received a great deal of attention due to its many advantages such as versatility, ease of operation, bactericidal effectiveness, and low cost, etc. The two most popular DSA electrodes are RuO2 and IrO2, as anodic materials. However, a conflicting observation has been reported in terms of chlorine evolution. The purpose of this study is to examine which DSA electrode, RuO2 or IrO2, is more effective for chlorine evolution with the same moles of Ru or Ir deposited on the surface of each electrode using the thermal decomposition method. The electrochemical properties, atomic composition, point of zero charges, binding energies, resistances, contact angles, and the active surface areas of RuO2 and IrO2 electrodes were examined as potential factors affecting chlorine evolution. The major results showed that the RuO2 electrode has higher electro-catalytic property for chlorine evolution than IrO2 electrode. This result was explained by the lower oxygen/metal atomic fraction, a more positive surface charge, lower binding energy, lower resistance, and more hydrophilic properties of RuO2 electrode than the IrO2 electrode.