According to the requirement of the butting short and middle waves long linear IRFPA detectors integrating and coupling with the inline pulse tube cryocooler, the difficulties of the Dewar package were discussed. By studying the temperature uniformity and the supporting structure of long butting substrate, the cold loss and the vacuum life of the large-size Dewar, the three-dimensional thermal output method of the multi-point "S" type thermlink combined with the conductive layer was proposed, and the supporting structure of "bridge" with the dual substrate was designed, which were to solve the key technologies of higher temperature uniformity of the long butting substrate, the lower thermal stress of the integrated detector and depth of focus control, space environmental adaptability, lower cold loss and longer vacuum life, the Dewar assembly for the dual-band long linear FPA had been successfully developed, and tested by serial space environment adaptability tests, the results show that those main performances do not change obviously. The Dewar assembly satisfys the requirements of the space application.