A model of the full-parallax holographic stereographic imaging system is built. The wavefront aberration exists because of the depth distribution of three-dimensional (3D) objects, and this aberration is analyzed by the related theory of diffraction-limited imaging system. Rectangular pupil is used as the exit pupil of the imaging system. The relationship among the optical transfer function (OTF), the spatial frequency, and the pupil size is obtained in such situations as non-aberration, small-aberration and large-aberration. In addition, the imaging quality can be evaluated by the integral values of OTF on spatial frequency, the variation relationship between the integral value of OTF and pupil size is obtained under different aberration conditions, so as to optimize the size of rectangular pupil and get the optimal aperture size on printing platform of full-parallax holographic stereogram to improve the imaging quality.