Abstract: The main factors that affect the phase measurement accuracy were analyzed and simulated in detail for the case of detecting high-density fringes by CCD in phase-shifting interferometry. The influences of the pixel size of CCD, random noise and sampling quantized lever of the intensity in interferogram were discussed. The results indicate that, with the increase of CCD pixel size and random noise's RMS, the signal to noise ratio of sequence intensity detected by CCD would be worse, and the phase measurement error is getting greater. When the signal to noise ratio is greater than about 24, the phase measurement accuracy could be better than π/50 rad, which is equivalent to the λ/100 better of optical path difference. This research provides a theoretical quantitative basis for the further study of extending the measuring range of phase-shifting interferometry.