In this thesis, we study the selective etching properties between as-deposited and crystalline phase of Ge2Sb2Te5 alloy film carried out with an alkaline etching solution of NaOH. The optical and physical properties of the thin films before and after etching are measured by Lycra spectrometer and surface profile. And we use the optical pump-probe system and atomic force microscopy (AFM) to manufacture the sample and investigate the topographic change. Through the complete experiments, results showed the etching of the crystalline film is fast than the as-deposited Ge2Sb2Te5 film. The disordered amorphous region acts as an resistant mask. A novel high throughput and low cost nanolithography method is developed by the Ge2Sb2Te5 phase-change masking thin films. The special Opto-thermal effect of phase-change material can be applied to the Nanolithography in the future.