A modified phenolic resin containing tertiary amine oxide was prepared via a two-step method. Epoxy phenolic resin, F-48, was reacted with dimethylamine to give the phenolic resin containing the tertiary amine group, which was then oxidized with hydrogen peroxide to obtain the target product. The tertiary amine oxide-containing resin could easily dissolve in water. However, it became water insoluble after heat treatment at a high temperature such as 160 °C. Thermal properties of the tertiary amine oxide resin were studied with DSC and TGA. A thermo-sensitive film comprising the prepared resin and an IR-dye was prepared and laser-induced thermal imaging was also conducted. This material might be used to develop new chemistry-free printing plates.