Abstract: High-precision measurement of thin-film is a precondition for the process optimization and diagnositcs in the thin-film preparation. Interferometric metrology is a widely accepted high-precison measurement technology which takes wavelength as the measurement unit. A novel measurement method of thin-film thickness based on phase-shift interferometry is presented. The precision measurement for the thickness of SiO2 thin-film sample was realized after the phase unwrapping and data processing for the obtained interferogram were implemented. The results show that this method has the advantages of noncontact and high accuracy, and the PV and RMS values of the measured thin-film thickness are 0.162μm and 0.043μm respectively.