Optical line protection system is combined of OLP-Optical Line Protection and operation maintenance terminal. It can realize optical power monitoring、optical line auto-switching and network management etc. In optical communication network, OLP monitors optical power of optical fiber and standby optical fiber at real time. In case the current optical power of optical fiber is less than pre-set switching threshold value, then alarm is on and it would switch to standby optical fiber automatically to protect optical transmission system line. OLP can provide a protection scheme for all routes and main lines easily with low cost, can protect all networks which needs optical line switching, all these above can make an optical communication network with no-block、high reliability、safety and high anti-disaster strength.