Cassegrain telescopic system has been widely employed in environmental observation such as in astrophysics and navigation. Currently available Cassegrain telescopic system mainly used aspheric mirror systems in order to gain satisfied imaging quality. However, aspheric mirror systems are difficult to fabricate and assemble. In the present study, an easier to be fabricated global Cassegrain telescopic system was designed by using the optical design software Zemax OpticStudio. The structure consists of a primary mirror with a hole, a secondary mirror, and four auxiliary lenses, which the F is 2.6 and the focal length is 760mm. Its wavelength can be operated from 0.9 to 1.7μm and the linear block ratio about 0.45. MTF within the frequency of 35 lp/mm is great than 0.5, and the size (Φ) is small than 350×800mm. According to the above specifications, the structure has a better imaging quality with better aberration correct capability. The proposed structure can provide a new way for designing Cassegrain reflectional telescopic optical systems.