To comprehensively analyze the jitter error in large-aperture optical telescopes, this paper introduces normalized point source sensitivity (PSSn) to evaluate the telescope system. First, the concept and basic properties of PSSn were introduced, and then the jitter error under expected random loads and the contribution percentage of each mode to the total jitter were analyzed through a model. The PSSn of the system under the influence of different error sources was studied, and its variation trend was estimated. A comparison of evaluation methods, such as the Strehl ratio, and the proposed method reflects the characteristics of more accurate data and a more concise calculation. The jitter error evaluation method proposed in this article, combined with PSSn, provides practical and beneficial guidance for the design and detection of large-aperture optical telescope systems.