Based on the power-series' and Zernike circle polynomials' decomposition theory of wavefront aberration, the relationship between Zernike circle polynomials and Seidel polynomials is illuminated. The correlation Zernike circle polynomials on the annular domain is analyzed theoratically, and the effect of central obscuration interferograms fitted with Zernike circle polynomials on calculating Seidel aberrations is emphasized. The experimental results are consistent with the theortical analysis,and a simple and intuitionistic enactment method of error tolerance is provided. With the increase of obscuration ratio, it is found that the error of Seidel coefficients is increased, and its changing rule dependes on the aberration type and magnitude of the optical element under test. When the obscuration ratio reachs a certain threshold value, the error curves would greatly change. For achieving the accurate Seidel coefficients, the order number of the Zernike circle polynomial fitting should be selected apporiately, and the Zernike annular polynomials should be selected in a large obscuration-ratio case. Additionaly, the effect of the obscuration ratio on the tilt and astigmatism along Seidel aberrations is less than that on the coma, focus and spherical terms.