As a typical Schmidt telescope, China Near Earth Object Survey Telescope (CNEOST) has the optical characteristics of short focal length, large field of view, and low spatial resolution. The optical system has a prime focus with a focal length of 1.8 m, the film scale of 9um/', and the geometric encircled energy concentration EE80 ≤2'. The diameter of the optical FOV (field of view) is 4.28-°(14.3deg2), and the observational FOV is 9deg2 with the equipment of the current 10k times 10k STA1600LN CCD (charge-coupled device) camera. In order to expand the observation capacity of the telescope, a secondary mirror and a field corrector are added in the original optical system, and the Cassegrain focus and Nasmyth focus with a focal length of 9m can be obtained. The diameter of the optical FOV of new focus is 15', and the geometric encircled energy concentration EE80 EE80≤0.5". It provides a prerequisite for high-resolution photography, spectrum, and high-precision multicolor photometry of solar system small bodies.