Abstract: The scattering correction is the key topics of high-precision crown measurement. In this paper, the theoretical model estimated method of point spread function (PSF) was used. First, the PSF Monte Carlo (MC) model was established to analyze the changes in the relationship of PSF with the source energy and the plate thickness. The calculation method with the results of several single energy was put forward to replace the spectrum calculation, and achieved good results. Then with the double-Gaussian model, combining MC simulation result, the PSF of crown measurement system under single energy source was analytically solved. And PSF theory formula under 0.18 MeV source energy was given, which lay the groundwork for the scattering correction of crown measurement system.