In this paper, the CM EMI of the three-phase Vienna PFC circuit is analyzed. By analyzing the EMI coupling path, the CM and DM EMI are separated. In view of the particularity of three-phase Vienna PFC topology, the problem of DM interference crosstalk and CM interference crosstalk is proposed, and the conversion of DM interference to CM interference is analyzed. For the characteristics of Vienna PFC circuit, the filtering effect and the dynamic response speed of the PFC circuit are taken into consideration. The design of the passive common mode EMI filter is given and the stability analysis is made. Finally, the performance of the passive common mode EMI filter is verified by simulation.