The invention discloses a distributed micrometeorological monitoring method for transmission lines, comprising the following steps: S1, a Brillouin optical time domain reflectometer is used to monitor the temperature distribution of a transmission line OPGW; S2, a calculating and data processing unit calculates the temperature gradient of each monitoring point on an overhead line in time according to the OPGW temperature spatial distribution obtained through multiple times of monitoring; S3, the calculating and data processing unit calculates the temperature gradient of the overhead line distributed in space according to the OPGW temperature spatial distribution obtained; S4, temporal temperature gradient thresholds and spatial temperature gradient thresholds under different rainfall conditions are set; and S5, the rainfall distribution information and rainfall size information of the transmission line are judged according to the temperature gradient distribution across the transmission line, and thus, distributed rainfall monitoring on the transmission line is realized. The monitoring method of the invention is characterized in that the method has a high degree of intelligence and enables a computer to easily and automatically analyze and judge the distributed rainfall information of a transmission line, and can be widely used in transmission lines.