We have calculated electron energy loss spectrum for electrons transmitted through a mask in projection electron lithography by Monte Carlo simulation based on the dielectric function model and Mott elastic scattering cross section. A good agreement between simulation and experiment is obtained. The calculation results of the transmission and contrast for the masks in scattering angular limitation for projection electron lithography show that the contrast is dominated by the thickness of scattering layer (thicker the scattering layer higher the contrast), but is less affected by the thickness of the supporting membrane. Furthermore, with the increasing aperture angle the transmission increases but the contrast reduces, and the contrast decreases with increasing primary energy of electrons.