Here presented the system of fast neutron radiography on Cockcroft-Walton Neutron Generator in China Institute of Atomic Energy,based on 14.1MeV neutron source.Its been done to investigate the position resolution of fast neutron radiography system to models made of polythylene,aluminum,iron and lead material,Indicates that the position resolution of system is better than 1mm level to a single material.About 2mm crack can been discriminated through a compound structure.It has been found that the fast neutron radiography effect will be subject to many restrictions and random disturbances: photographic images in a variety of noise and the background of the problem further different sources of noise were analysis(such as: neutron scattering noise,collimator channel activation,neutron imaging screen with the crosstalk between the proton and neutron scattering induced CCD camera flare).