In order to mearsure emerging wavefront and dynamic wavefront of optical system, a point diffraction interferometry based on technique for demodulating circular carrier interferogram is proposed. Circular carrier is introduced in interferogram by shifting point diffraction plate in longitudinal direction in conventional point diffraction interferometer. The circular carrier interferogram is converted into quasi linear carrier interferogram after quadratic polar coordinate transforming, meanwhile the continuous spectrum is converted into quasi discrete spectrum in frequency domain. Fourier transform method is then applied to extract phase. Simulated wavefront is generated randomly based on 36 Zernike polynomials, and root mean square value of phase recovery error is 0.002l on condition that defocus is 17l. Testing the emerging wavefront of F/10 lens is realized by using this method and the result is in agreement with that obtained by SID-4 wavefront sensor; dynamic measuring of organic glass absorptive character is also realized . This method can be applied to test optical system and measure real-time wavefront.