Referring to the experimental parameters, the physical model of neutron radiography with 14MeV neutrons is built and the process of radiography is simulated using the Monte Carlo method. Effect of neutron scattering by a polyethylene sample on radiography is analyzed as a function of d, the distance between the sample and the detector, and parameters of the sample. The calculated results indicates that for a d values smaller than 5cm, intensity of scattered neutron component strongly depends on d, while when d is greater than 20cm, the influence of scattered neutrons to the image is reduced to a negligible level. The results also indicates that the effect of neutron scattering is relatively large when density of the sample ranges from 3g/cm3 to 5g/cm3, and intensity of scattered neutron component increases with width of the sample and is almost saturated at width greater than 3cm.