Abstract: The deficiencies in traditional H-D curve measurements in high-energy flash X-ray radiography are analyzed and the relationship between the optical density and X-ray exposure is obtained using Monte Carlo simulations. A spherical symmetrical object is used to obtain an optical density profile. Various factors, which lead to asymmetrical distribution of the optical density, are analyzed using Monte Carlo simulations. It is shown that the main factor is the imperfect geometrical alignment of radiographic parts such as collimator and electron beam axial. Averaging the leftright optical density of symmetrical points is a reasonable method. And the method to obtain H-D curves is detailed, and accurate H-D curves are presented according to Silberstein theory. This measurement avoided the measu