Abstract: The fluorescent converter used for fast neutron radiography was developed by using the home-made wavelength-shifting fibers (WSF). As the experiment shows, the luminosity of the WSF converter is 6-8 times as high as that of the converter we used before and the statistics of the imaging is much better. The relationship between the luminosity and the thickness of the WSF converter is also obtained from which the saturation thickness is 25 mm. The smallest defect that can be detected by the converter is about 2 mm.