The optical properties of monocrystalline silicon are crucial for the performance of short- and medium-wave infrared detection systems, and they significantly impact the advancement of aerospace technology. The thermal stress problem caused by temperature gradient in preparing monocrystalline silicon by the Czochralski method is focused on in this paper, and the influence of thermal stress on the optical inhomogeneity of monocrystalline silicon is examined. By comparing the stress birefringence phenomenon of monocrystalline silicon under three different methods of no thermal annealing, slow thermal annealing, and rapid thermal annealing, the infrared absorption and refractive index characteristics of monocrystalline silicon in the near-infrared band (3~5μm) are deeply analyzed. The influence of different annealing methods on the optical inhomogeneity of monocrystalline silicon is summarized. Herein, the elucidation of the stress-induced effects on optical uniformity is reported and present a strategy aimed at enhancing optical uniformity is presented through stress reduction in the monocrystalline silicon. This work lays the theoretical groundwork and offers practical insights for the fabrication of high-quality monocrystalline silicon.