Abstract: An optical system of digital X-ray radiography based on CsI scintillation screen with 60 mm45 mm dimension for dental diagnosis was designed. A CCD with a 4.8 mm3.6 mm image surface was selected. The lens system had a complicated double-Gauss configuration. The F# and full field of view were up to F/0.9 and 35 respectively, the focal length was 9mm. The results showed that the modulation transformation function of full field of view was greater than 0. 75 at the spatial frequency of 56 lp/mm, the distortion of full field of view was 1.8%, and the relative illumination reached 80%.The aberrations of the whole system were corrected, which met the requirements for the digital X-ray radiography system.