A kind of test method of optical surface with big curvature on the plane interferometer is mainly studied, the measured surface error relative to the standard plane appointed has been obtained by some pivotal techniques such as interference fringe processing, fast Fourier transform (FFT) phase distilling, phase unwrapping and Zernike polynomial fitting, then it subtracts the standard spherical surface appointed, so the measured surface error relative to the standard sphere appointed has been obtained by reusing Zernike polynomial. On the basis, PV, RMS, N, ΔN of the measured surface error are calculated, the interference fringe formed by the measured surface relative to the standard sphere is successfully simulated. The method overcomes the disadvantages of contact test, and provides a suitable method particularly to optical surface with high precision and big curvature radius.