Abstract: The paper introduced design methods of two repeaters of CAN bus, namely hard repeater and soft repeater. Hard repeater has simple circuit but short transmission distance or small transmission rate of CAN bus. Soft repeater uses CPU to transfer data with convenient upgrading and has data filtering function to decrease bus load, but which is not suitable for CAN bus system with high requirement of time sequence. Both of the repeaters are verified at field and should be selected according to actual system.