Abstract: For the interferometric testing of optical elements with large aperture, due to large testing device and interferometric cavity length, the process of phaseshifting interferometry was affected by airflow disturbance and environmental vibration. In order to overcome the above factors, a single interferogram processing method based on two-dimensional fast Fourier transform(FFT) was proposed. This method only required one single spatial carrier fringe pattern to obtain the phase, which had the advantage of anti-vibration testing. The basic principle and the process of algorithm were analyzed, and the optical element with 600 mm large aperture in the near-infrared phase-shifting Fizeau interferometer was tested. Experimental results show that the peaktovalley (PV) value and root mean square (RMS) value of the wavefront obtained by FFT method are 0.112 and 0.014 respectively, compared with the results obtained by phase-shifting method, there are a difference less tham (1/500) in PV and almost zero difference in RMS.