Abstract: Automotive motor is one of the electromagnetic interference（EMI）sources in automobile，it belongs to broadband interference source. Taking automotive air conditioner motor as example，the author studied the mechanism，testing method and suppressing measure of electromagnetic interference of automotive DC motor，also provided a electromagnetic compatibility （EMC） filter circuit，and the interference character of the circuit was tested and analyzed. The results showed the filter circuit can effectively suppress the differential mode interference and common mode interference of the automotive air conditioner motor，improve the filtering performance，make the conducted interference voltage and the radiated interference voltage satisfy the EN 55014-1∶2006+A1∶2009+A2∶2011 standard.

Key words: electromagnetic compatibility （EMC）, conducted interference, radiated interference, differential mode interference, common mode interference, DC motor