Abstract: The reliability of high-precision extended-area blackbody products in complex high-low temperature environments currently fails to meet practical application requirements. Furthermore, their operational lifespan under extreme conditions is shorter compared to similar foreign products, which severely restricts applied research in related fields. To address these issues, this study analyzes the impact and effects of environmental factors on blackbody reliability based on the working principles, functional requirements, and structural composition of extended-area blackbodies. Specific investigations are conducted on the thermal stress and structural stability of Peltier devices. Finally, measures are proposed to enhance the reliability of high-precision extended-area blackbodies in complex temperature environments, including the adoption of process-optimized Peltier devices to mitigate thermal stress and the stabilization of multi-layer clamping structures. The analysis and conclusions presented in this paper provide valuable insights for improving the reliability of such devices in extreme temperature conditions.