Abstract: In view of the application requirements of miniaturized micro-Dewar packaging for large- or ultra-large-array cooled infrared detectors (hereinafter referred to as detectors), as well as the long-term in-orbit operation and power cycling conditions of aerospace detectors, this study investigates the factors affecting the reliability of heat transfer coupling in large-diameter cold-finger insertion structures through experimental analysis and theoretical calculation. The results indicate that, to ensure the reliability of long-term in-orbit operation of space probes, several key factors must be considered in the design of the Dewar insertion-type coupled heat transfer structure of the detector. These include controlling the temperature fluctuation of the Dewar hot end within ± 3 ℃ and maintaining the simulated gap between the end face of the refrigeration cold finger and the inner end face of the Dewar cold finger below 15 μm at low temperatures. The side gap between the refrigeration machine cold finger and the Dewar cold finger should be controlled within the range of 0.05–0.15 mm, and the ratio of the top surface area to the side surface area of the refrigeration machine cold finger copper cap should be maintained below 40%. In addition, indium sheets and thermal grease are introduced at the interface between the end face of the refrigeration machine cold finger and that of the Dewar cold finger while ensuring an appropriate level of coupling interference. By analyzing and controlling the above factors, a large-diameter cold finger insertion coupling component for the detector was developed, and long-term operational testing with repeated power-on and power-off cycles was conducted. The results show that the detector completed more than 7000 cycles of power-on and power-off operations while maintaining normal functionality.