Aiming at the packaging requirements of large scale infrared detectors, the design methods and characteristics of cold box packaging structure are introduced in this paper. According to the use and demand of different types of large scale infrared detector assemblies, their packaging structure, weight, thermal load and reliability are analyzed and studied, and the packaging structure of large scale infrared detector assembly is optimized. Lightweight and low power consumption are taken as the design idea, and the packaging structure is optimized by the finite element simulation tool to meet the design requirements.