Abstract: Imaging performances of neutron radiography detectors, which consist of neutron-optical photon converter, image optics subsystem and CCD camera, were analyzed elaborately. Firstly, the variation of detective efficiency with the thickness of scintillator and the difference on quantum gain of two typical coupling methods between converter and CCD were discussed. Secondly, modulation transfer function and detective quantum efficiency with different lens coupling methods were described. Lastly, noise equivalent number of quanta was introduced to compare radiography detectors in theory.