Laser patterning technology of indium tin oxide thin films has been studied in this research. ITO thin films, which usually coat on the glass and the plastic substrate, have been adopted in the flat panel displays (FPDs) and the plasma display planes. The conventional method of the ITO patterning usually uses the wet chemical etching processing. However, the wet etching processing is not adopted in the plastic materials because the chemical fluid usually damages the plastic substrate. The laser direct writing processing has been developed and replaces the wet etching processing. This investigation is interested in the laser patterning used the third-harmonic Nd:YAG laser (355 nm) to ablate the ITO films of glass substrate. The scanning electron microscope (SEM) measures the characterization of the ablated grooves used the different parameters, including the laser energy, the repetition rate and the feeding speed of the table. Finally, the effect parameters of laser ablating ITO film will be presented in this paper.