Based on the principle of Hartmann wavefront analyzer (HWA), the necessity of calibrating pinholes array to CCD spacing LH is clarified. The method of calibrating LH with known gradient plane wave, and tracing gradient value to the point source accuracy displacement, is presented and discussed. According to this calibration method, a HWA is calibrated and corrected value of LH is given. The calibrated HWA measures three spherical wavefronts with different curvature radii. Compared to ideal spherical wavefronts, wavefront measurement accuracy is up to λ/35 , and wavefront aberration peak- valley (PV) value is λ/7 . The experimental results show that calibrated value of HWA is accurate, and given calibration method is effective and feasible.