The development of remote sensing satellites has made Spaceborne cryocooler used more widely, the cryocooler provides the required temperature environment for the detector, but also brings micro-vibration interference which will affect the performance of detector. Therefore, it is necessary to suppress the micro-vibration of cryocooler. In this paper, a passive vibration isolation device for cryocooler is designed based on relaxation damper and layout of three-point uniform support, the isolation performance of the device is analyzed. The transfer characteristics of dynamic model and finite element model are compared. The result shows that the vibration isolation efficiency of the designed passive vibration isolation device for the main frequency, double frequency and triple frequency can achieve 90%,95% and 97%. This paper can provide significant reference for designing such kind of passive vibration isolation device for sapceborne cryocooler.