Abstract: The basic principle of projected fringes deflectometry is to measure the point-o-oint relations of coordinates among free-orm surface, camera and projection screen, and then compute the reconstructed surface with calculated slope data iteratively. In order to reduce the calculating time of the wavefront reconstruction without losing accuracy, a fast Fourier transform(FFT)Zernike combined algorithm was proposed. The simulated result demonstrates the proposed algorithm can decrease the iterative procedure to 5 times using less than 20 seconds, compared with the traditional Zernike modal algorithm which has 15 iteration times using more than 1 minute. In addition, the calculating time is cut by two-hirds with the accuracy achieving the order of nanometer.