A technique combined multi-wavelength phase-shifting interferometry with principal component analysis (PCA) is presented. By using a monochrome CCD to simultaneously capture a sequence of in-line phaseshifting interferograms with random and unknown phase shifts at multiple wavelengths, the wrapped phase information of each wavelength can be constructed through using the PCA algorithm. Then an unambiguous phase of an extended synthetic beat wavelength can be determined by multi-wavelength optical phase unwrapping and noise reduction. Both the numerical simulation and experimental results show the simple optical measurement process, fast computing speed and high resolution of the proposed method.