The invention discloses an optical fiber operation monitoring method and system under extremely cold weather conditions. The optical fiber operation monitoring method or system under the extremely cold weather conditions disclosed by the invention is realized mainly through a data interface layer, a data processing layer, an operation analysis layer and a monitoring center; wherein the data interface layer collects operation data in real time and sends the operation data up to the data processing layer; the data processing layer establishes a first database through receiving the operation dataand processing the operation data in a standardized manner, and transmits the data of the first database up to the operation analysis layer after encapsulating; the operation analysis layer establishes a second database according to the corresponding relationship between the change of temperature and the change of optical power of the optical fiber after de-encapsulating the encapsulation data, and transmits the data in the second database up to the monitoring center. Through monitoring the optical power of the optical fiber, the corresponding relationship between the change of the extremelycold low temperature and the change of the optical power is established, the danger threshold is set up to carry out fault warning, and the early warning fault position and operation condition are accurately judged; therefore, the occurrence of the failures threatening the whole network can be avoided effectively.