This application provides a narrowband interference isolation method and a communication apparatus. An example method includes: determining a parameter of a narrowband interference signal; determining a coefficient of a first filter based on the parameter of the narrowband interference signal, wherein the first filter is located at a receive end of a master communication device, and the coefficient of the first filter is for filtering out the narrowband interference signal; and sending the parameter of the narrowband interference signal or the coefficient of the first filter to M slave communication devices using an Ethernet operation, administration, and maintenance (OAM) frame, wherein the master communication device is connected to the M slave communication devices, M≥1, and M is an integer.