The invention provides a method and apparatus for detecting the link state. The method is applied to a central processing unit of an optical fiber communication device, the optical fiber communication device also comprises at least one port group, each port group at least includes one transmitting port and one receiving port, and modes of the port group of the optical fiber communication device comprise a single-fiber mode a double-fiber mode. The method includes: receiving a link detection instruction; obtaining a target port group whose port group mode is the single-fiber mode in the at least one port group; and switching the port group mode of the target port group to the double-fiber mode, and detecting the link state corresponding to the target port group in the double-fiber mode. By employing the method and apparatus, the mode of the port group is switched to the double-fiber mode from the single-fiber mode, the detection of the link state in the single-fiber mode is realized by employing the link detection process in the double-fiber mode, and communication failure caused by non-equivalence of the link real state and the default state is avoided.