High energy electron radiography is a useful nondestructive method for density material diagnosis. The higher the kinetic energy, the stronger penetrability the electron has. Thus electron with GeV energy is considered for probing the density material. This paper aims at 2.5 GeV electron radiography. The key processes of radiography are studied by Monte Carlo simulation. All simulations are carried out by Geant4 code. Firstly, basic physical processes including the transport of electrons in the quadrupole lens group and the attenuation of the interaction between electrons and matter are constructed by Geant4 code. Some details about the physics setup are given. Four samples of different materials and thickness, with voids inside, are designed as the object of simulation radiography. Other necessary geometries for electronic photography such as quadrupole and pixel detector are built as well. Then a large-scale electronic photography is simulated. In addition to this, two step samples made of copper and tungsten, respectively, are employed as object for the radiography simulation. In the simulation, collimated line electron source radiates objects, then the line spread function of the electron beam passing through the different area density is obtained. Based on the simulated results, evaluation about the detection and resolution ability of 2.5 GeV electron radiography is shown.