An optical system of Dome-screen projector which plays important roll in the pilot-training process was proposed. The lens system adopted the Reverse-Telephoto configuration which had an effective focal length of 5.5mm,an F-number of F/4,a field of view of 175°,and a working wavelength in the range of visible spectrum. A discussion about the relationship between the screen radius and the field curve was presented to explain why this system had an advantage in reducing the field curve. A relatively convenient method of choosing the appropriate screen radius was given at the end of the discussion.