Cryocooler is an important equipment to provide low temperature working environment for infrared device. However, its driving system′s conducted interference severely affects the precision of the infrared loading. It′s not easy to analyze the common-mode part included in conducted interference. To study the common-mode interference mechanism, based on an existing infrared system project′s cryocooler and its driving system, the mechanism was quantitatively analyzd using a new multi-physics co-simulation method and the model′s accuracy was verified by specific experiment measurement. Finally, the characteristic of disturbance pathway and source were analyzed and the mechanism of the common-mode interference was concluded. Results show that, the parasitic parameter of the cryocooler is the most important factor of transmission path within the range of test frequency. However, with frequency increase, the effect of cable′s parasitic parameter is increasing and can′t be ignored. The interference mechanism concludes that the common mode interference produced by system may induce the overrun of the CE102 standard from 500 kHz to 1 MHz.