Abstract: X-ray pinhole imaging is an important diagnostic tool in inertial confinement fusion (ICF). The point spread function (PSF) of the X-ray pinhole imaging can be used to restore the initial image and estimate the spatial resolution. This paper analyzes relations among X-ray wavelength, size of pinhole aperture, magnification and also simplified Fresnel diffraction formula. The PSF of the X-ray pinhole imaging was derived numerically using Fresnel diffraction integral. Fresnel diffraction simulated the optimal pinhole aperture, X-ray wavelength and magnification with optimal spatial resolutions and an excellent signal-to-noise ratio. The calibration of the sample was used to gain the modulation transfer function (MTF) of the whole framing camera imaging system, and Fresnel diffraction simulated the PSF of the pinhole imaging, so the PSF of the framing camera was deduced. We also obtained the PSF of the framing camera by measuring its edge function, the two results were unanimous and showed the method to stimulate X-ray pinhole imaging by using Fresnel diffraction is feasible.