Because the phase-shifting point diffraction interferometer (PS/PDI) uses lateral shearing of test and reference waves to generate carrier frequency fringe pattern, significant systematic measurement errors are consequentialty introduced. A new calibration method of PS/PDI systematic errors, named rotating grating method, is proposed. Based on the PS/PDI measurement results obtained with two gratings in orthogonal directions, the proposed method utilizes the orthogonal and symmetric property of Zernike polynomials in unit circle to calibrate the systematic errors of PS/PDI. The calibration experiment of visible light PS/PDI is performed to verify the method. The result shows that the geometric coma of the system is －0.116 λ which is consistent with the theoretical value of －0.133 λ, which proves the validity of the method.