MCNP simulation method of neutron radiography is introduced.The process that Maxwell thermal neutron penetrates the samples is simulated,and clear images are obtained.The contrast of simulation results and actual neutron radiography is also given.The simulation images are very similar to the experimental images.The analyse of the effect of scattered neutrons is included.As the distance between objects and scintillation screen increases, the scattered component decreases. For a distance of double object size, the influence of the scattered neutrons to the image can be ignored.The ability that thermal neutrons penetrates Al,Pb,Fe and Cu is discussed.The reason for the difference between simulation and experimental results is studied.The conclusion can be drawn that the MCNP simulation method