A thiol compound with a long hydrocarbon chain was introduced into the developing solution for a silver chloride DTR printing plate. It was found that the hydrophobicity of physically developed silver area could be greatly improved. The higher the silver density and thiol concentration were, the greater the hydrophobicity of the silver surface was. Raman and XPS study revealed that hydrophobization was caused by adsorption of the thiol compound on physically developed silver particles on the plate.