High quality pseudo-thermal sources are essential in X-ray ghost imaging microscopic applications. The pseudo-thermal source used in X-ray Fourier-transform ghost imaging is obtained by modulating X-ray with a screen full of randomly distributed holes. The statistical properties of the X-ray speckle fields are analyzed based on the statistical optics, and the influence of the screen parameters is explored by numerical simulations. Results show that the optimum contrast for ghost imaging can be achieved when the phase difference introduced by the screen is π. For random amplitude screens, the imaging contrast increases with the decrease of the duty cycle, while for random phase screens, the imaging contrast decreases with the decrease of the duty cycle. In practical X-ray Fourier-transform ghost imaging systems, the screen made of metal can be treated as a complex amplitude screen, and the high-contrast ghost imaging can be realized by choosing appropriate transmittance and duty cycle of the screen.