Abstract: The distance between the charge couple-device (CCD) and the micro lens array is one of the assembling errors which affects the accuracy of HartmannShack wavefront detector. The correction of this motion assembly parameter can effectively reduce the wavefront detector error. The relationship between the subaperture spot centroid shift amount,caused by the spherical wavefront passing through the micro lens, and the structural parameters of wavefront sensor was derived theoretically. By utilizing the relationship, it is able to work out the actual distance from the CCD to the micro lens array and improve the calculation of the slope of wavefront. Experiments verified the rationality of theoretical derivation, and the actual assembly parameter calibrated is 24.2 mm. The wavefront was reconstructed by the calibrated parameter, the relative error can reduce by 20.4%. Experiment results show that the calibration method can effectively improve the measurement accuracy of wavefront sensor.