In order to measure multiband radiation characteristic of objects, a tripleband optical imaging system working in 300～1 000 nm range was designed, which shared the same optical window. In this system, two right-angle prisms were used to split light of different waves, and each band used independent optical lens. This system can obtain images at the same time in the wavebands of ultraviolet, visible and infrared. The ghost image of the system was simulated and analyzed with the help of Lighttools software. It is shown that there are multiple ghost images which reduce the contrast ratio of the images on the surface of detector, because of light multiple reflected between the surfaces of right-angle prism and window. Experimental results show that the tripleband optical imaging system can achieve good image quality, and the ghost images can be cleared away when the angle of the optical window and the first prism is controlled in seven seconds. The efforts of this paper are referable for research and design of multiband optical imaging system using prism to split light.