In order to have a better understanding of the optical properties of segmented telescope system and conduct an effective analysis of the impacts of various errors induced by single segmented mirror of primary mirror, this article aims at builting a model of segmented telescope system from the perspective of geometry optical with optical raying tracing. This model enables to simulate the segmented telescope of different sizes, and can get the wavefront aberration and the far-field image of the segmented telescope with the piston error, tip-tilt and rotation error ect. Strehl ratio of segmented telescope with different errors is calculated. The work is expected to provide technological support for the further development of large diameter telescopes.