The design method of ARM and CAN interface circuit on a new IED is introduced. When developing a new IED based on ARM microprocessor and uClinux operating system, CAN fieldbus was selected considering the field-level communication requirements of substation automation systems with high reliability and real-time performance. Since the CAN transceiver SJA1000 is an address and data time-sharing multiplexing chip, and the address line and data line of ARM are separated, the software simulation timing method is adopted, and the read and write signal of SJA1000 is generated by using the I/O pin of ARM, the hardware interface circuit of ARM and CAN is designed, the driver of CAN under uClinux is written, and the debugging pass. The design of this interface lays a good software and hardware foundation for the communication of new intelligent IEDs, which can better adapt to the needs of substation automation systems.