Point spread function (PSF) defines the intensity of the diffraction image formed by the optical system for a point source. The PSF of an optical system varies with the field of the point source and such variance generally cannot be neglected. This paper proposes a realization method of full-field PSF—incorporating field dependence into the PSF matrix. Two practical optical systems with distinct degree of aberrations are chosen and the PSF using the method proposed with that obtained by direct integration are compared. The result and analysis suggest this method can obtain the PSF in any desired field at a fast speed and with relatively high accuracy.