The present subject matter relates to the field of communications technologies, and in particular, to a method and an apparatus for indicating a fault in flexible Ethernet. The method for indicating a fault includes: detecting whether a fault occurs in at least one physical layer entity included in a flexible Ethernet group; and when a fault occurs in the at least one physical layer entity, periodically sending a fault indication code block to a flexible Ethernet client corresponding to the at least one physical layer entity in which the fault occurs. Not all bandwidth of a downstream transmission path in the flexible Ethernet is occupied, and data transmission on a non-faulty channel in a same flexible Ethernet group is not affected, thereby reducing a quantity of affected flexible Ethernet clients.