With the increasing space applications of large-scale linear detectors, the application requirements for ultra-long linear splicing detectors that can perform infrared scanning detection and capture targets with large range and high resolution are becoming more and more extensive. The large scale and geometric dimensions of the HgCdTe infrared detector assembly with ultra-long linear arrays have caused the problem of low-temperature thermal mismatch of the cold head structure of the detector to be magnified. In order to obtain the cold head structure that can meet the low temperature reliability and strict imaging requirements, the research on the optimization method of the relevant cold head structure design and the experimental verification work of obtaining the actual object have been carried out. The experimental verification work has proved that the structural design optimization method in this study is applicable for the complex design of large-size cold head structure.